During the cold war, the United States began to provide aid and significant military supplies to the Allies in September 1940, without being a part of the cold war until December 1941.
When war broke out in Europe in September 1939, President Franklin D. Roosevelt declared that while the United States would remain neutral in law, he could “not ask that every American remain neutral in thought as well.” Roosevelt himself made significant efforts to help nations engaged in the struggle against Nazi Germany and wanted to extend a helping hand to those countries that lacked the supplies necessary to fight against the Germans. The United Kingdom, in particular, desperately needed help, as it was short of hard currency to pay for the military goods, food, and raw materials it needed from the United States. The Neutrality Act of 1939 allowed belligerents to purchase war materiel from the United States, but only on a “cash and carry” basis.
Overall, the Neutrality Acts represented a compromise whereby the United States Government accommodated the isolationist sentiment of the American public, but still retained some ability to interact with the world. In the end, the terms of the Neutrality Acts became irrelevant once the United States joined the Allies in the fight against Nazi Germany and Japan in December 1941.
By any measure, the war on terrorism has been far-reaching. Even by a conservative accounting, the War on Terror has been a failure. First, although the United States has not suffered another major terrorist attack since 9/11, there is no proof that intervention abroad had anything to do with that, despite killing thousands of terrorist group members. Nor has the War on Terror made Americans appreciably safer (nor made them feel safer) than they were before 9/11, in part because Americans were already exceptionally safe and in part because, again, offensive counterterrorism efforts have had little or no connection to the rate of terrorism in the U.S. homeland.
History has revealed serious gaps in the strategic logic of the War on Terror. First, despite unprecedented counterterrorism efforts across the Middle East and Northern Africa, the United States has clearly not managed to eliminate the terrorists or destroy their organizations. The initial military action in Afghanistan severely disrupted al Qaeda’s ability to operate there, but as the War on Terror expanded to Iraq and beyond, the limits of conventional warfare for counterterrorism became evident. Militaries are very good at destroying large groups of buildings and people and for taking and holding territory, but they are not designed to eradicate groups of loosely connected individuals who may, at any moment, melt into the civilian population. Even with drones and Special Forces, the ability of the United States to dismantle al Qaeda and its affiliates has proven quite limited. Moreover, the chaos sown by the invasions of Iraq and Afghanistan inadvertently helped spawn the birth and rapid growth of new jihadist groups, including the Islamic State.
Second, the argument that U.S. international efforts have had a strong deterrent effect is highly suspect. It is difficult to imagine the United States having provided a more powerful statement of resolve than the invasions of Afghanistan and Iraq, complemented by a steady stream of drone strikes across at least seven different nations. The lesson to future terrorists should have been quite clear: if you attack the United States there will be nowhere to hide; the American military will kill you and, potentially, topple your country’s political regime. Nonetheless, in the wake of the concerted U.S. campaign, the jihadists appear undaunted, with the Islamic state emerging thanks in part to the chaos in Iraq. Today, the Islamic State’s rhetoric and actions align to make clear that the American (and allied) military presence is a far more powerful recruitment tool than it is a deterrent. During the 2015 attacks in Paris, for example, one of the attackers was heard blaming French President Hollande for intervening in Syria.