On Monday, Secretary of Defense Chuck Hagel announced massive cuts to the size of the armed services, slashing the army to its pre-World War II size. In 2011, the army had some 566,000 soldiers; Hagel wants it cut to somewhere between 440,000 and 450,000 troops by 2019. If Congress does not add additional funding, Hagel threatens to slash that number to 420,000 by 2019.

Such cuts to defense spending do not bode well for the security of the United States. Historically, defense spending cuts have preceded increased international turmoil as America’s global enemies sense a failure of will. A senior Pentagon official leak to The New York Times betrayed precisely that failure of will: “You have to always keep your institution prepared, but you can’t carry a large land-war Defense Department when there is no large land war.” And the Times added that the proposal is designed to defeat “any adversary,” but prevent the military from engaging in any “protracted foreign occupation.”

So, how big are the current cuts? Historically speaking, they’re incredibly large. In 2011, the defense budget represented 4.7% of total gross domestic product; this year’s percentage will be 2.7%. In real dollars, US defense spending is set to plummet from $705.6 in 2011 billion to $496 billion. That represents a budget cut of approximately 30%.

The Pre-World War II Cuts. While FDR increased government spending in virtually every other area of American life, FDR slashed defense spending from the beginning of his administration, from $752 million in 1932 to $531 million in 1934. He even cut veterans’ benefits 40%. By the time of World War II, America was thoroughly unprepared to make war, with an army sized just smaller than that of Portugal, ranking 16th on the planet. That unwillingness to fund defense led both Hitler and the Japanese to believe they could make war on the United States with impunity.

The Post-World War II Cuts. After World War II, during which the United States spent 43.6% of its annual GDP on defense in 1943 and 1944, spending declined dramatically – all the way down to 14.3% of the annual GDP in 1949. The era of peace and prosperity seemed that it would last forever; Harry Truman justified defense cuts by citing the end of World War II. But then the Korean War broke out, thanks in large part to the large-scale military cuts, which encouraged the Soviets and Chinese Communists toward aggression on the Korean peninsula. Truman then increased the defense budget from $9.1 billion in 1948 to $52.8 billion, a nearly six-fold increase. Again, that could have been prevented had the United States been less eager to take a machete to defense budgeting.

The Vietnam Cuts. As the United States consolidated its victory in Vietnam, Democrats in Congress, angry at the re-election of President Richard Nixon, decided to defund the military. Where defense spending had represented an average of 19.6% of GDP during the period 1967 through 1972, the budget really began falling after 1968 and the election of Richard Nixon. The result: American helicopters lifting off from our embassy in Saigon as the country fell into Communist hands. The Soviets would invade Afghanistan just a few years later, encouraged by America’s obvious distaste for foreign war. Only the arrival of Ronald Reagan and his huge increases in military expenditures would change the shape of the Cold War.

The Post-Soviet Defense Cuts. In 1988, the United States government spent $557.5 billion (in inflation-adjusted 2011 dollars) on national defense. That statistic slowly declined under George H.W. Bush, to $489.2 billion in 1992 – but then it collapsed under Bill Clinton, who slashed the military budget to $378.5 billion. That cut of 32% is slightly larger than the cut proposed here, but it also took place over the course of 11 years rather than the three. The defense cuts provided a temporary economic boost, given that defense spending was siphoned into other areas of the government, decreasing overall government spending. But it also paved the way for the rise of al Qaeda – a disastrous malfeasance that led to 9/11, and the tremendous military buildup under George W. Bush, under whom military spending rose from $397.3 billion in 2000 to $701.1 billion in 2009.

If the United States had maintained its spending under Ronald Reagan, it is possible that the attacks of 9/11 – presaged by Islamic terror attacks on multiple American targets beginning with the first bombing of the World Trade Center in 1993 – would have been stopped. Had that occurred, the United States would have never needed to nearly double its spending on defense. Even if the attacks had not been prevented, the United States would have been significantly better prepared for the counterinsurgencies in Iraq and Afghanistan than they were during the military build-up period at the beginning of the Bush administration.

Overall, major defense cuts come with a serious price: the price of emboldened enemies. Unfortunately, the cuts contemplated by Chuck Hagel and company have already borne fruit in an emboldened China in the South China Sea, a resurgent Vladimir Putin-led Russia, an aggressively Islamist Middle East. The problem with military cuts is not merely that they decrease American capacity to make war, though they surely do. The problem is that purposeful and large-scale military decreases send a message to the rest of the world that America is in retreat.

Sadly, under the Obama administration, that signal is both clear and correctly interpreted.

Ben Shapiro is Senior Editor-At-Large of Breitbart News and author of the New York Times bestseller “Bullies: How the Left’s Culture of Fear and Intimidation Silences America” (Threshold Editions, January 8, 2013). He is also Editor-in-Chief of TruthRevolt.org. Follow Ben Shapiro on Twitter @benshapiro.