Today's terrorists can not match Gavrilo Princip.

When the nineteen-year old member of the Black Hand shot the Archduke of Serbia and his wife, he didn't kill just two royals. He triggered World War I ... and more than 37 million causalities.

Of course, it wasn't all Princip's doing -- the world was primed for war. The sun was setting on the British Empire. Regional powers had been carving up the globe. Confident in their vast industrial resources, these modern nation states were ready to fight. Its commercial dominance and sea power slipping, Britain could no longer keep the peace. The conditions for conflict were set.

Decisions made over the last two years have moved the world closer to a 1914-like setting. Historians like Paul Kennedy blame conflict and the decline of great powers on "overreach," arguing that regimes strain their economies trying to defend themselves and then implode or are pushed over in an orgy of violence.

But Kennedy has it backward. Great powers collapse not because defense becomes too costly, but because their economies cease to flourish and they can not afford to defend themselves.

This could well be the fate the United States. Our sluggish economy cannot sustain the lavish government programs we've created. Yet politicians shrink from putting politically popular entitlement programs on a fiscally sound basis. Instead, they label these programs "nondiscretionary" -- even though they are driving the deficit.

And so they focus on "discretionary" spending programs, as though they are all far more, and equally, expendable. Defense funding is lumped in this category, and serious defense analysts agree that if the Pentagon suffers additional cuts of $500 billion or more in the next round of deficit reduction, the U.S. will simply cease to be the military power that it is today.

Unfortunately, under the deficit ceiling deal, that is Plan B. If that happens, our "nuclear triad" (bombers, and sea- and land-based missiles) will disappear. Three Navy Battle Carrier groups could get mothballed. The Air Force would lose four fighter wings. The Marine Corps might have no large-scale amphibious capability. The active Army could lose all of its heavy-armored forces.

In short order, the U.S. will unable to protect the freedom of the commons (the capacity to move around the globe by land, sea, air and cyberspace) that allowed goods, peoples and ideas to move around the world.

Regional powers, though unable to surpass us, could push us aside in their part of the world. Most of these powers (think China) won't share our interests, values or worldview -- much as the Kaiser's Germany differed from Edwardian Britain.

And when quite different powers find themselves in parts of the world where their interests touch, conflict arises. When no one power can overmatch the other, they seek to balance -- by dealing and double-dealing with other powers.

One day in this very unstable future, a Gavrilo Princip or Osama bin Laden will come along and set the world on fire. Only this time, with today's modern weapons, billions will die.

There are only two paths away from this future. One would be if all the "future" great powers embraced economic freedom, justice and liberty -- seeking to compete without conflict. Sadly, the rise of China, the relapse of Russia, and the economic and moral collapse of Europe suggest this is unlikely.

The only other path demands a resurgent America that continues the mission it played in the 20th century -- giving the future and freedom a chance.

An American renaissance requires a budget deal that makes the fiscal reforms needed to let the economy grow and prosper without gutting the military. That's a tall order -- but it beats fighting World War III.

James Jay Carafano is a senior research fellow for national security at the Heritage Foundation.