Palestinian groups were enthusiastic participants in Soviet terror largesse. General Alexander Sakharovsky, head of the KGB's First Chief Directorate, famously said in 1971, "Airplane hijacking is my own invention," referring to the Palestinian Liberation Organization's hijackings. In the 1950s and 60s there was, on average, five hijackings a year; in 1969, Palestinian terrorists hijacked 82 aircraft. George Habash's Popular Front for the Liberation of Palestine was crucial. The secular, left-wing Habash boasted, "Killing one Jew far away from the field of battle is more effective than killing a hundred Jews on the field of battle, because it attracts more attention."

When the Soviet Union ended, so did much of the secular, left-wing terrorism it had sponsored. Logistical support, funding, and advice all stopped. But, just as importantly, the intellectual, spiritual, and philosophical engine of leftist terror had become broken and powerless. Communism did not work; liberal democracy and capitalism had won. Marxism lost its inspirational impact without a superpower cheerleader and benefactor. The potential terrorists were no longer motivated by Marxism and, crucially, neither were their supporters.

Terrorism has always been about more than the terrorists themselves. The perpetrators need a motivating ideology to justify their crimes, as well as committed enablers around them. The enablers themselves require a broader base of political supporters and advocates -- "the useful idiots" (an expression credited to Lenin). In the early 1970s, one poll reported that a tenth of Germans under the age of 40 said they would shelter members of terrorist group Baader-Meinhof; a quarter expressed their broad support, even after Baader-Meinhof had murdered over 30 people, including police officers, newspaper workers, and businessmen. With the fall of the Soviet Union and the collapse of communism, extreme leftism lost its inspiration and the terrorists lost their support. Baader-Meinhof announced its own disbandment in 1998, five years after its last terrorist attack and seven years after the Soviet Union disbanded.

Terrorism, however, did not go away.

Many of the next generation of terrorists found inspiration in the founding narrative of Islam, of Mohammed and his few but dedicated supporters affecting massive political change against impossible odds. While this is perverse to the vast majority of Muslims, some genuine grievances helped broaden political support for that agenda among a wider population. Cheap and easy air travel, fluid financial systems, and especially the flow of information over the Internet enabled a greater reach than in the 70s.

Whatever else it is, al-Qaeda was an inspiration, with an agenda easily adopted by willing "franchisees." State support still continues. Elements of the Pakistani military continue to assist terrorist organizations in Indian Kashmir and in Afghanistan. Iran and Syria continued in a similar fashion, sponsoring operations in support of foreign policy objectives within their neighbors' territories.

The lesson of Soviet-sponsored terror and its end is that, if the world is to defeat Islamist terrorism, it will have to defeat the motivating narrative. In the same way that communism became a bankrupt ideology, the political philosophy underpinning terrorism needs to be challenged, exposed, and ridiculed.

Nick Lockwood is a British post-conflict expert, specializing in population engagement and stability operations, and an Adjunct Fellow at the American Security Project.

We want to hear what you think about this article. Submit a letter to the editor or write to letters@theatlantic.com.