Yet as many states achieved independence from colonial powers following World War II, the numbers of Christian missionaries kept increasing. In 1970, according to the Center for the Study of Global Christianity, there were 240,000 foreign Christian missionaries worldwide. In 2000, that number had grown to 440,000. And by 2013, the center was discussing in a report the trend of “reverse mission, where younger churches in the Global South are sending missionaries to Europe,” even as the numbers being sent from the Global North were “declining significantly.” The report noted that nearly half of the top 20 mission-sending countries in 2010 were in the Global South, including Brazil, India, the Philippines, and Mexico.

As the center of gravity of mission work shifts, the profile of a typical Christian missionary is changing—and so is the definition of their mission work, which historically tended to center on the explicit goal of converting people to Christianity. While some denominations, particularly evangelicalism, continue to emphasize this, Christian missionaries nowadays are relatively less inclined to tell others about their faith by handing out translated Bibles, and more likely to show it through their work—often a tangible social project, for example in the context of a humanitarian crisis. Humanitarian work has long been part of the Christian mission experience, but it can now take precedence over the work of preaching; some missions do not involve proselytizing in any significant way. “It’s not to say that no one ever does any preaching—of course they do,” said Melani McAlister, a George Washington University professor who writes about missionaries, “but the notion that ‘our main goal is to convert people’ has been much less common among more liberal missionaries.” Instead, undertaking mission work can entail serving as a doctor, an aid worker, an English teacher, a farmer’s helper, or a pilot flying to another country to help a crew build wells. Many missionaries I’ve spoken to say they hope their actions, and not necessarily explicit words, will inspire others to join them.

“When I’m abroad I don’t use the word ‘missionary’ because of the stigma that it carries with other communities,” Jennifer Taylor, a 38-year-old missionary in Ukraine, told me recently. “I just usually use ‘volunteer’ or ‘English teacher’ so it actually sounds like I’m there with a purpose, and I’m not going to make you believe something you don’t want to believe.” She considers it her job to model a life with purpose, which she hopes can lead people to embrace Christianity without it having to be forced down their throat.

Beyond faith, Christian missionaries’ motivations can vary widely, in part because they come from diverse denominations. Mormons, Pentecostals, evangelicals, Baptists, and Catholics all do mission work. The work is particularly central to Mormonism, which encourages observation of the scriptural invocation to “preach the gospel to every creature.” Pentecostals and evangelicals are also among the more visible. (By way of comparison, at the beginning of this year, 67,000 Mormons from around the world were serving as missionaries, while the U.S.-based Southern Baptist Convention reported having sent only about 3,500 missionaries overseas.) They may be driven by their faith, the wish to do good in the world, and an interest in serving a higher purpose. But their motivations, according to young Christian missionaries I’ve spoken to, also include everything from the desire to travel abroad to the desire for social capital. Often, these are mutually reinforcing.