Around the world -- from the southern United States to the Middle East -- religion is on the rise. It is growing in countries with a wide variety of religious traditions and levels of economic development, suggesting that neither poverty nor social exclusion is solely responsible. The religious resurgence is not simply defined by the growth of fundamentalism -- rigid adherence to a particular set of rituals and doctrines -- but is occurring through a variety of renewed rituals and practices, both public and private.

Demographics are reinforcing this trend. The global religious landscape in the coming years will be affected by the massive shift in population growth from the developed countries of the North -- predominantly in western Europe and the former Soviet republics -- to the developing countries of the so-called global South. The North accounted for 32 percent of the world's population in 1900, 25 percent in 1970, and about 18 percent in 2000. By 2050, it will likely account for just 10 percent. Religion has emerged as a driving factor in this redistribution. Religiosity is now one of the most accurate indicators of fertility, far more telling than denominational or ethnic identity, since religious people tend to have more children than their secular counterparts.

Religion will also increasingly be an urban phenomenon. The growing population in the developing nations will mostly settle in vast, burgeoning, and largely impoverished metropolises -- areas where religion is spreading. According to conventional wisdom, secularization became an inevitable part of modernization with the spread of education, science, technology, and prosperity. But these new megacities are havens for religious revivals. Historically, religions have been adept at gaining adherents in urban environments; Christianity formed as an urban religious movement in the cities of the Roman Empire, and the Franciscans began as an urban reform movement in medieval Europe in response to the poverty and inequality accompanying the rise of the market economy. Islam may follow the same path by expanding in urban environments. Although urbanization can lead to civil unrest and cities can provide cover for criminal and terrorist networks, urbanization also offers well-meaning religious institutions opportunities for urban ministry that could help prevent such threats in the first place.

Another aspect of the religious resurgence is the disintegrating relationship between the West and Christianity. Traditionally seen as a Western or European religion steeped in that continent's culture, Christianity evolved from its Jewish origins in Palestine, conquered the pagan world, and spread east to Iraq, India, and China before the Mongol invasions reduced it to its European setting. It is now returning to its roots by becoming a post-Western religion dominated by the peoples, cultures, and countries of the global South. For U.S. policymakers -- many of whom currently consider Islamism to be the most urgent religious challenge to Washington's foreign policy -- the politics of global Christianity may soon prove just as pivotal.

A variety of trends, including demographic shifts, urbanization, and the global transformation of religion, indicate that religion will help shape the dynamics of existing, new, and emerging great powers, influencing U.S. attempts to promote freedom, civil society, democracy, social cohesion, and economic development across the world. Globalization's transformational effect on religion will also play a key role in the prevalence of global terrorism, religious conflict, and other threats to international security.

CHRISTIAN AND ISLAMIC RESURGENCE

The most dramatic religious explosion in the world today is the spread of Pentecostalism and evangelical Protestantism. It is part of the demographic shift toward the global South and a key factor in Christianity's worldwide transition. Pentecostals and evangelicals share many of the same core beliefs: they subscribe to the authority of the Bible (often interpreting it literally) and believe in the need to proselytize to non-Christians.

According to a 2006 report by the Center for the Study of Global Christianity, the number of evangelicals worldwide, including Pentecostals, is estimated to range from 250 million to 688 million. After Catholics, Pentecostals represent the largest single group of Christians. They live predominantly in Brazil, China, India, Indonesia, Nigeria, the Philippines, and the United States, but they also enjoy a presence in Chile, Ghana, Guatemala, South Africa, and South Korea.

The explosion of Pentecostalism and evangelical Christianity has collided with entrenched religious communities. Three countries with substantial Muslim communities -- India, Indonesia, and Nigeria -- also have large Pentecostal populations and sizable minorities of Christians more broadly. Muslim-Christian tensions have recently arisen in those nations, most notably in Nigeria, where sectarian violence erupted earlier this year and left over 500 people dead.

Pentecostalism and evangelical Christianity appeal across class lines. Their message of God's love, hope, and consolation attracts the occupants of shantytowns in many megacities, and their inspiring themes of forgiveness and personal transformation through a sober, frugal lifestyle blends with middle-class values around the world. Once thought of as highly personal religions with little interest in politics, Pentecostalism and evangelical Christianity have become more politically active -- particularly in Latin America, where Pentecostal and evangelical candidates largely support democracy and lobby for religious freedom in heavily Catholic countries. But their biblical literalism can also motivate religious intolerance. Either way, Pentecostals and evangelicals will be a major religious, social, and political force in the coming century.

Islam is also experiencing a genuine revival, one that extends beyond the more extreme Islamic fundamentalist movements. More Muslim women are wearing the veil, more Muslim men are growing beards, and more Muslims are attending mosques more often. According to the Gallup Center for Muslim Studies, Islam is thriving, with 86 percent of Turks, 90 percent of Indonesians, and 98 percent of Egyptians surveyed reporting that religion plays an important part in their lives.

The Islamic world extends far beyond the Arab world. It is therefore difficult to generalize about Islam's position regarding women, democracy, capitalism, or terrorism. Yet much as Westerners must attempt to understand the facets of Pentecostal and evangelical Christian growth, they will need to make the same effort in striving to understand the global spread of Islam.

RELIGIOUS RENEWAL IN ASIA

Remarkably, given its Marxist past, China is experiencing a tremendous expansion of Pentecostalism and evangelical Christianity. The Center for the Study of Global Christianity projects that there may be 218 million Christians in China by 2050, perhaps 16 percent of its total population. The current Pentecostal and evangelical populations are concentrated among the growing middle class. Protestantism spread rapidly in China only after the communist government expelled foreign missionaries between 1949 and 1953, making its spread almost entirely indigenous. Now primarily concerned with its economic development, China tacitly allows established religions -- Christianity and neo-Confucianism -- to operate relatively freely, believing that they can promote social harmony amid rapid social changes. The question for China is whether this domestic tranquility will continue. If Christianity achieves the kind of cultural permeation of China that it has in South Korea -- where it has reached over a quarter of the population -- it could fundamentally alter China's political fabric.

Meanwhile, northwestern China is home to over 20 million Muslims and is now in the grip of an Islamic reawakening. Chinese authorities are concerned about the young Chinese Muslims now studying across the Middle East, and especially in Saudi Arabia, whose rigid Wahhabi institutions are offering educational scholarships and bringing Chinese Muslims under their influence. Ethnic minority Uighur Muslims and Han Chinese have clashed violently in the western province of Xinjiang. Deeply concerned about their country's fragmentation, China's leaders are adamant about preventing a separate Islamic enclave from gaining autonomy in the western half of the country. The rise of Christianity and Islam in China, then, will color discussions about political stability, democracy, human rights, and foreign policy there for years to come.

The rest of Asia is also experiencing dynamic religious changes. In contrast to religion in the West, religion in Asia is less individualistic, more communal, and more socially embedded. Thus, religious vitality appears consistent with secular politics in a variety of politically modernizing states -- China, Indonesia, Japan, South Korea, and Taiwan. The same religious diversity is spreading to India. Although over 80 percent of Indians are Hindus, this dominance masks considerable religious variation across India's states. Muslims comprise 67 percent of the population of Jammu and Kashmir. Christians predominate in India's small eastern states of Nagaland (90 percent), Mizoram (87 percent), and Meghalaya (70 percent) and are significant minorities in two southern states, Kerala (25 percent) and Tamil Nadu (6 percent). Sikhs make up nearly 60 percent of the population in Punjab.

Long-standing social tensions within India -- most notably in relation to the country's caste system -- also have a significant interreligious dimension. In particular, the movement for the rights of Dalits, the country's lowest caste, known as "untouchables," has long been complicated by Dalit religious conversions, often from Hinduism to evangelical Christianity. This has angered Hindu nationalists, leading to Hindu-Christian tensions. Despite these internal conflicts, India remains a model of a large, vibrant, successful, deeply religious, and multiethnic democracy outside the West.

RUSSIA AND THE ORTHODOX CHURCH

In Russia, meanwhile, Orthodox Christianity is enjoying a revival after 70 years of communist suppression. Few have appreciated the depth of the damage caused first by communism and then by corruption in the post-Soviet era -- they undermined trust, integrity, and accountability, as well as moral and cultural values, in the country.

The Russian Orthodox Church is now aiming to restore these values and overcome modernization's atomizing effects on post-Soviet Russian society. According to a 2004 study by the Kennan Institute, the Orthodox Church is Russia's second most trusted institution, behind the presidency, with far greater credibility than the media, the police, the army, or the overall government. It has formed an alliance around these goals with fellow religious organizations, a partnership that has the potential to be an important part of civil society. Yet Russians must still determine what freedom of religion means for a country that is predominantly Orthodox. A debate is also taking place within and outside the Orthodox Church itself over the nature of human rights -- whether they are consistent with Orthodoxy or are cultural imports from the West -- and their appropriate place in modern Russia.

The Orthodox Church's role is especially crucial given that cultural and political power seem intertwined in modern Russia. The church's attempt to unify its domestic and overseas hierarchies in the wake of Soviet rule and its increasingly close relationship with the Russian state have established a type of Russian Orthodox identity politics. The Moscow Patriarchate of the Russian Orthodox Church is one of a number of "autocephalous" (literally, "self-headed," meaning "independent") churches within Orthodoxy, and it sees the reunification of the church's various branches as an important step in spreading the patriarchate's influence worldwide. The Russian state, meanwhile, views reunification as a means to boost ties between Russia proper and the Russian diaspora as part of its quest to regain global power. Although the Orthodox Church claims that it has no wish to serve as an organ of the state, its relationship with the Russian government will play a major role in Russia's near-term future.

Muslims are also an important force in Russia, making up between 12 and 15 percent of the population. Russia has more Muslim inhabitants than any other country in Europe. Battles with Muslims in the North Caucasus -- Chechnya, Dagestan, and Ingushetia -- have left Moscow viewing Islam as a source of extremism, separatism, and secession. The Russian Orthodox Church has had a checkered relationship with Islam, dating back over 700 years, but current problems between the two religions are fed by more recent phenomena. These include Orthodox fears of Islamic extremism and renewed notions of an Islamic-Christian struggle, which first emerged from the Soviet war in Afghanistan and then from the regional struggles following the collapse of the Soviet Union.

GLOBALIZED RELIGION

All these trends are inherently intertwined with globalization and highlight its tendency to create a more unified and yet more fragmented world. Global and local religious identities are becoming linked because globalization is changing the very nature of religion and its role in international affairs. Ever since Samuel Huntington popularized the notion of a "clash of civilizations" in these pages, many accounts of the world's religions have cast each religion as a vast, static bloc linked together by culture, theology, and territory. Up to a point, Huntington was broadly right. Religions often have intersected with specific cultures, states, and territories. In Europe, this reality was reinforced by the Treaty of Westphalia in 1648, which essentially privatized religion to the realm of individual belief and nationalized it as the basis for organizing modern states. Later on, European colonialists attempted to interpret Hinduism and Buddhism through the lens of Protestant theology, exporting their understanding of religion, culture, and territory to the developing world.

But religions have seldom operated as static blocs with set beliefs. They have always been adaptable and in flux, shaped by and shaping their surroundings. In his new book Holy Ignorance, Olivier Roy argues that globalization is facilitating the detachment of religion, culture, and territory, thus unraveling religious traditions from particular cultures and nationalities. Roy points to global religious movements such as Salafism, a militantly literalistic form of Islam; Pentecostalism; and evangelical Christianity to contend that fundamentalism is particularly well suited to globalization because its claim of a universal truth is inherently disconnected from particular states and societies. Whether or not the other groups he references -- Tablighi Jamaat (the largest transnational Islamic organization in the world), China's Falun Gong, and Sri Lanka's Theravada Buddhism -- can be considered fundamentalist, they have joined existing global religious traditions, such as the Roman Catholic Church and the various Orthodox patriarchates, in impacting international relations.

Globalization is also making religion more pluralistic. The kind of religious monopolies that have benefited the Orthodox churches in central Europe, the Catholic Church in Latin America, and Hinduism in India will be difficult to sustain. Religion is increasingly, if unevenly, becoming a matter of choices -- about whether to believe, whether to embrace one particular kind of religion, and, if so, what elements or sect of that religion to embrace. Religion is no longer imposed or taken for granted by prevailing cultures. The debates in the new Iraqi parliament and increasingly in many other Muslim countries -- over the lines between Islamic law and religious freedom, the role of women in society, and regulations regarding conversion and proselytizing -- indicate that this shift is also taking place in the Islamic world.

Globalization also gives greater influence to ethnic and religious diasporas. These communities are contributing to the changing nature of international security and are one of the most significant types of nonstate actors in international relations. Globalization has blurred the lines between religious organizations involved in advocacy, proselytizing, or social welfare -- for example, Tablighi Jamaat or Hezbollah -- and purely terrorist organizations. It is these kinds of both local and global social networks that allow people to support or facilitate the operations of al Qaeda, Hamas, and other illicit groups across the world.

Yet the mixing of sacred and secular objectives in religious institutions is nothing new. Piety and political struggle have often accompanied each other in developing countries. Sufi brotherhoods in North Africa, for example, supported Islamic resistance fighters against French occupation in the nineteenth century.

Westerners find this blending of religion and politics uncomfortable. But in the religious world of the global South, there is often an overlap between social, charitable, political, and even terrorist networks. In weak and failed states, which are plagued by corruption and crumbling social infrastructure, a variety of charities and faith-based organizations will remain a main source of education, social welfare, and health care.

Globalization also enables members of diasporas to join religious groups in their countries of ethnic origin. The Internet and cheap airplane tickets, for example, give young, rootless, and alienated Muslims in the diaspora the opportunity to construct new, radical identities by joining a virtual ummah, or global Islamic community. One recent example is Faisal Shahzad, the so-called Times Square bomber. A Pakistani-born immigrant who lived in Connecticut, Shahzad nonetheless visited Pakistan often and received terrorist training from the Taliban.

Simmering local conflicts could, if allowed to fester, lend fodder to extremists arguing that Islam and Christianity, or Buddhism and Islam, are at war. This has happened in Buddhist Thailand, where an Islamic separatist insurgency is raging in the south, and it is happening in the Philippines, where a long-running Islamic independence movement has linked itself with al Qaeda in recent years. In both places, isolated revolts have taken on international proportions as war zones within a larger battle.

FAITH AND FOREIGN POLICY

As the world becomes more religious, religion will also likely alter relations in the traditional nation-state system. At a basic level, religion will be an important factor in understanding the general foreign policy orientations of many countries. There will undoubtedly be exceptions -- Western states supported Muslims in Bosnia and Kosovo over Christians, to take one instance -- but many historical examples suggest that religion reinforces collective identities and guides foreign policy. Germany's Catholics pressured the country to recognize Catholic Croatia's secession from Yugoslavia in the aftermath of the Cold War. Orthodox states such as Greece and Russia opposed NATO's bombing of Orthodox Serbia in 1999. Russia's claims of political influence over the Ukraine are related to the fact that Uniats, also known as Eastern Rite Catholics, dominate its western territories and are at odds with the Russian Orthodox Church.

The foreign policy implications of religion are evident when it comes to Islam as well. Saudi Arabia's cultural diplomacy has consolidated the country's influence in the Islamic world by spreading its more rigid form of Islam, upsetting local Islamic practices and long-standing traditions of religious toleration and coexistence. Meanwhile, Iran has pursued an equally aggressive religious diplomacy, exporting its messianic form of Shiism across the Arab world and supporting sectarian movements in Lebanon (Hezbollah), the Palestinian territories (Hamas), and Iraq.

Another potentially important factor in international relations is the impact of Christianity on foreign policy orientation. The political scientist Walter Russell Mead has argued that the global rise of Christianity is good for U.S. foreign policy. Christianity, he says, is "the world's most pro-American faith" because it is congruent with American beliefs and ideas (if not always actions), supports religious freedom, and helps inculcate the kind of values conducive to democracy and economic development.

Mead is partly correct, although perhaps not for the reasons that he cites. U.S. foreign policy is increasingly influenced by the way globalization creates or empowers new types of collective identity and political action, including global Pentecostalism and evangelical Christianity. Globalization enables Muslims and Christians in the global South to link their local conflicts to competing global narratives. Islamic and Christian nonstate actors -- for example, Franklin Graham's Christian relief organization, Samaritan's Purse, now active in the Sudan -- draw on diasporas to provide them with financial and political support. American Christian values and goals connect the United States to societies and countries in the global South with Pentecostal or evangelical constituencies. The religious dimensions of this kind of collective identity and transnationalism is a growing feature of U.S. foreign policy and explains (to a large extent) legislation in the past decade on human trafficking, religious freedom, the violence in Darfur, and human rights in North Korea.

Yet Mead's vision of Pentecostalism and evangelical Christianity boosting the status of the United States in foreign countries is not a foregone conclusion. Given the increasingly indigenous development of these Christian groups in non-Western countries, they have embraced local concerns and local politics in places such as China. Pentecostalism and evangelical Christianity are certainly not monolithic, and it remains unclear whether Christians in the global South will align with their more conservative U.S. counterparts on foreign policy issues. On the issue of the Iraq war, for example, they did not. Meanwhile, evangelicals in China seem more inclined to follow Chinese nationalist sentiment than to embrace the United States.

It is possible that religion in the global South will not reflect Western political categories. For both Muslims and Christians in developing countries, religion is likely to be more socially conservative than in the West, taking a harsher stance on abortion and homosexuality. At the same time, religion in the global South could be more politically liberal, since people in developing nations are generally more concerned with poverty, economic justice, and the environment; more skeptical of capitalism and globalization; and more supportive of the United Nations and international law.

Globalization and its impact on religious trends will undoubtedly affect domestic conditions as well. Religiously divided populations from Indonesia to Nigeria have clashed in recent years, and fresh Muslim-Christian conflicts are erupting in Côte d'Ivoire and Kenya. Statistics on civil unrest indicate that once a minority religious group in a given country reaches 10-20 percent of the population, it can sufficiently resist policies promoting religious harmony and can even sustain struggles for liberation.

Clearly, other factors contribute to such strife besides religion. Yet although many conflicts are the result of politics, economics, and governmental mismanagement, religious ideas do matter. Collective action depends on how social groups perceive the world in which they live and how they view their own identities in relation to the identities of others. The way religious institutions address literacy, schooling, governance, human rights, and interreligious dialogue can support governments' ability to respond to crises surrounding these issues or exacerbate religious strife.

RELIGION IN THE WORLD AHEAD

A new kind of world is in the making, and the people, states, and religious communities that compose the global South are making it. The major world religions are all taking advantage of the opportunities provided by globalization to transform their messages and reach a new global audience.

Faith informs the daily struggles of millions in confronting larger political conflicts regarding democracy, human rights, and economic development. Ethnic and religious diasporas in the global South are connected to the West in ways that can create or reinvigorate collective identities, whose influence can both promote social welfare and fuel terrorism and interreligious conflict. As a result, understanding religions worldwide -- their beliefs, values, and practices and the way they influence the political goals, actions, and motivations of states and religious communities -- will be an important task for U.S. and international foreign-policy makers in the coming decades. If the United States recognizes and utilizes the worldwide religious resurgence, it can harness its power to improve international security and better the lives of millions. If the United States fails to confront the implications of this religious rise properly, however, the potential for religiously motivated violence across the globe may increase dramatically over the next century.