With more than $4 trillion in federal budget deficits over the last three years and more than $3 trillion projected over the next four, there’s good reason for concern over runaway government spending.

Of the $3.8 trillion in 2011, about two-thirds is so-called “mandatory” spending. This includes a cornucopia of social “entitlement” programs on budgetary auto-pilot led by Social Security, Medicare and Medicaid, along with interest on the national debt. The rest of the budget is classified as “discretionary” spending, the largest component of which is the military.

Leftists always rail against military spending, and now is no exception. Yes, Defense Secretary Robert Gates has proposed modest defense cuts ($78 billion spread over five years), but he’s doing so at the behest of his boss, President Obama. The notion that we can make any substantial steps toward budget balance at the expense of national defense is a delusion. The elephant in the room is social spending. Discretionary spending is just over a third of the budget, and defense spending is just over half of that, which puts the military’s share of total federal spending at less than one-fifth. About 40 percent of that one-fifth is personnel expenses, and we’re already undermanned.

Aging equipment, especially aircraft, needs to be modernized, and equipment damaged or destroyed in Iraq and Afghanistan needs to be replaced. The U.S. Navy is down to 287 ships, 45 percent fewer than the 529 it had in 1991. Even if you slashed the defense budget by $100 billion in one year — an outrageously irresponsible act in these perilous times — that would have cut 2010’s $1.5 trillion deficit by only 6 percent.

Writing in The Wall Street Journal, Mark Helprin recalled that President Obama, in a speech at West Point last summer, cited our lagging economy as justification for sharp cuts in defense spending when he claimed, “At no time in human history has a nation of diminished economic vitality maintained its military and political primacy.” Huh? How about the United States? Still struggling through the Great Depression, in World War II we ramped up defense spending to 40 percent of GDP and 85 percent of the budget by 1945 in order to save the world from Nazi Germany and Imperial Japan, emerging as a free and economically stronger nation.

For the benefit of those with no knowledge of history who claim our current level of defense spending is unsustainable, here are some benchmarks: In 1960, when John F. Kennedy was elected — after the Korean War and before Vietnam — defense spending was 52 percent of the budget and 9 percent of GDP. In the 1980s, Ronald Reagan’s defense build-up, which ultimately defeated the Soviet Union in the Cold War, averaged 26 percent of the budget and 6 percent of GDP. Today, defense spending is 19 percent of the budget and 5 percent of GDP.

By contrast, social spending (what the Office of Management and Budget categorizes as “payments for individuals”) was a mere 26 percent of the budget in 1960. By 1989, the year Reagan left office, it was 47 percent. Today, it’s 64 percent, and growing. In 1960, non-defense spending was 8 percent of GDP; today it’s 20 percent. And that’s only at the federal level, not including state and local spending for social programs and government employees. This, not defense spending, is what’s driving the U.S. and the Euro- socialist democracies (that spend a lot less on defense) toward bankruptcy.

Providing for the national defense is the single most essential responsibility of our federal government, without which we have nothing — no freedom, no treasure, no country. The only thing more expensive than war is losing one. Leon Trotsky got one thing right when he observed that, “You may not be interested in war, but war is interested in you.”

Mike Rosen’s radio show airs weekdays from 9 a.m. to noon on 850-KOA.