Blowback is a term now broadly used in espionage to describe the unintended consequences of covert operations. Because the public generally is unaware of secret operations, the consequences transpire as a surprise, apparently random and without cause, and blowback results.
In its strictest terms, blowback was originally informational only and referred to consequences that resulted when an intelligence agency participated in foreign media manipulation, which was then reported by domestic news sources in other countries as accepted facts. In looser terms, it can encompass all operational aspects. In this context, it can thus mean retaliation as the result of actions undertaken by nations. The phrase is believed to have been coined by the CIA, in reference to the shrapnel that often flies back when shooting an automatic firearm.
In the 1980s, blowback became a central focus of the debate over the Reagan Doctrine, which advocated militarily supporting resistance movements opposing Soviet-supported, communist governments. In one case, covert funding of the Contras in Nicaragua would lead to the Iran-Contra Affair, while overt support led to a World Court ruling against the United States in Nicaragua v. United States.
Critics of the Reagan Doctrine argued that blowback was unavoidable, and that, through the doctrine, the United States was inflaming wars in the Third World. Doctrine advocates, principally at the conservative Heritage Foundation, responded that support for anti-communist resistance movements would lead to a "correlation of forces," which would topple communist regimes without significant retaliatory consequence to the United States, while simultaneously altering the global balance of power in the Cold War.
Given prior CIA support -- with military hardware, funding, and direct training -- of the Islamic insurgency in Afghanistan during the 1980s and also of Osama bin Laden, the September 11, 2001 Terrorist Attack is the most prominent contemporary example of blowback, because this U.S. support actually helped build bin Laden's terrorist organization in Afghanistan. In 1986, for example, the CIA built a training complex and storage facility for bin Laden outside the Afghan city of Khost, where bin Laden subsequently trained 35,000 volunteers, a site that continued in operation until it was ordered bombed by President Bill Clinton in August of 1998.