Speaking at the National Prayer Breakfast on February 5, President Barack Obama cautioned against judging recent barbaric attacks by ISIS as unique to Islam. He pointed to, among other things, depredations committed by Crusaders over 900 years ago.

Despite the blundering butchery by semi-barbarous European feudal armies, the medieval Crusades made strategic sense. After the fall of the Roman Empire and Western Europe’s descent into the Dark Ages, the Christian Byzantine Empire formed a protective shield against Muslim incursions into the Balkans and westward. In 1095, after Seljuk Turks overran much of the Byzantine Empire and occupied Christian holy sites in Jerusalem, Pope Urban II’s call for Crusades proved a historic turning point.

The day after Obama’s prayer breakfast lecture, his national security advisor, Susan Rice, speaking at the Brookings Institute, previewed the White House’s 2015 National Security Policy by calling for “perspective” in addressing “dangerous … numerous and varied” threats which, according to her, “are not of an existential nature.” She then incorrectly cited World War II as one of the existential threats to the United States before correctly noting the Cold War presented such a threat.

America at arms excels in crusades fought to a definitive conclusion. There have been several such “crusades” in American history and three existential threats.

The fight for independence from Britain constituted a struggle for existence that, had the patriots lost, would have aborted the American republic. After a long, hard struggle the patriots prevailed; failure would have meant the gallows. From the patriots’ perspective, theirs was a war for survival against formidable odds fought to a definitive conclusion. While not a “crusade,” it was a desperate fight. For the British, not so much—and they lost.

The American Civil War posed an existential threat not because the Confederacy wanted to conquer the Union, but because its success would have destroyed the Union. It was a closely run war but, in the end, the Union embarked on a two-edged crusade to preserve the Union and abolish slavery. The “Battle Hymn of the Republic” says a lot about President Abraham Lincoln’s determination and Washington’s war aims. While Gen. Ulysses S. Grant destroyed Confederate armies, Gen. William T. Sherman undertook offensives in Alabama and Georgia that sacked farms and destroyed industries to collapse the South’s already weak economy. The Union crusade preserved the United States of America.

The Second World War, too, was an American crusade, although Imperial Japan, Nazi Germany, and Italy never posed an existential threat to the United States. Japan sought to compel the United States to withdraw from the western Pacific. While a victorious Nazi Germany would have imposed a barbaric new “Dark Age” on Europe, in the 1940s the Nazis could not threaten the existence of the United States. Nevertheless, President Franklin D. Roosevelt mounted a crusade to save civilization that the American military pursued to a definitive conclusion. Japan and the European fascist powers suffered the same fate as the Confederacy: defeated armies, wrecked economies, devastated cities, disestablished political systems, and their countries occupied during political reconstruction.

The Cold War, however, posed an existential threat. Marxist ideology fostered a showdown between two incompatible socio-economic systems. The Cold War mobilized America’s industrial, scientific and academic communities. Although the nation was drawn into two indecisive conflicts in Korea and Vietnam, the overarching Cold War paradigm involved a struggle between antithetical systems, only one of which could survive. In the end, the genius of President Ronald Reagan was to label the Soviet Union an “Evil Empire” and undertake the largest peacetime military buildup in American history coupled with his strategic defense initiative—“Star Wars.” The overregulated and inept Soviet economy collapsed along with its ideologically bankrupted Marxist political system. Although Russia survived and will challenge the West again, because of Ronald Reagan, millions of Eastern Europeans were freed from political servitude. A crusading America makes for an awesome adversary.

The Obama administration’s refusal to recognize the existential nature of the threat posed by Islamic fanaticism does not make that threat less real. Given their apocalyptic vision, if al Qaeda’s rapidly metastasizing franchises obtain weapons of mass destruction, they will use them. ISIS computer specialists demonstrated remarkable information age capabilities in their 22-minute Internet presentation culminating in the live immolation of Jordanian Air Force Lt. Moaz al Kasasbeh. The nature of cyber warfare is that savvy hackers can wreak catastrophic damage. This existential threat is real. Given the fanatical commitment driving this threat, efforts to “decimate and contain” will fail.

What is needed is an American-led crusade to attack and annihilate al Qaeda and its ISIS franchise.

Dr. Earl Tilford is a military historian and fellow for the Middle East & terrorism with The Center for Vision & Values at Grove City College.