Like a foghorn's deep, loud warning to mariners who can't see the lighthouse or shoals ahead, the need to spend more on America's military forces is breaking through Washington's haze of misguided thinking.

Why else would both the chairman of the Joint Chiefs of Staff and the chief of staff of the Air Force call for spending at least 4 percent of our gross domestic product on defense, and two members of Congress introduce a joint resolution saying basically the same thing?

Because they understand that, unless we invest at least that much each year for five to 10 years in state-of-the-art technologies and platforms, our military will lose its fighting edge.

The warning signs are there. Today, when the Army goes to war, it does so with a force designed to fight the Soviets in Europe, not asymmetric warfare in the desert. The U.S. Air Force has some 2,500 fewer aircraft today than in the late 1980s, and the U.S. Navy fleet has less than one-half the number of ships it did then. Many of our weapons and systems are worn out or, worse, obsolete.

We are rapidly approaching the tipping point. A military ill-equipped for battle will suffer needless deaths. It's happened to our troops before, and it could happen again.

In 1950, some 400 young U.S. soldiers - many teenagers - watched a column of North Korean T-34 tanks advance. Only days before, these men had been on occupation duty in Japan.

Wet weather knocked out their World War II-era radios and soaked their sneakers (there hadn't been enough combat boots at the supply depot to go around). Each soldier carried only 120 rounds of rifle ammunition and a dozen were armed with Howitzers and "bazooka" rocket launchers. These weapons were effective during World War II, but they were no match for the heavily armored T-34s.

Nevertheless, they were ordered to engage the enemy. Gen. Douglas MacArthur said an "arrogant display of strength" was all it would take to drive back the "barefoot Asian army" of North Korea. Not quite. The men suffered 181 casualties.

This disaster was a failure of Washington leadership after World War II. Congress drastically slashed defense spending and, as a consequence, the military was simply unable to prepare for the next war.

This is not an isolated incident.

Today, our military faces similar obstacles. The number, size and duration of deployments have increased dramatically since the Cold War, yet defense spending remains historically low. Take the procurement budget: During the Reagan buildup (fiscal years 1981 through 1985), we spent an average of $131 billion a year. During the post-Cold War procurement holiday, mean defense spending was $71 billion between 1990 and 1997, and in the war on terrorism, the mean has been $93 billion for 2002 through 2011.

The "peace dividend" of the 1990s, coupled with the intense wear-and-tear on equipment, is creating a perfect storm. We're paying today's military bills at the expense of tomorrow's readiness.

If and when the pace of operations in Iraq slows, we'll hear increasing calls to slash defense spending again. But unless Congress keeps the money flowing, our military could degenerate into a hollow force. That's what happens when military readiness declines, and funding levels are simply inadequate to support ongoing operations, to keep other forces trained and ready, and to modernize for tomorrow's threats at the same time. Choices have to be made.

The National Guard and Reserves are usually the first to show signs of being hollow. In 2005, mirroring the heavy reliance on reserve forces in Korea, the Army National Guard contributed nearly half of all troops on the ground in Iraq, and it has assumed a vastly increased role in homeland defense.

It faces severe equipment shortages. What's available is typically much older, more expensive and difficult to maintain, and not easily deployable. National Guard leadership has confirmed that from July 2002 through September 2005, overall unit readiness decreased 41 percent in order to provide personnel and equipment to deploying units.

Funding for immediate operations is beginning to come at the expense of the services' long-term health. There is only one way to properly equip and modernize our forces, and that is by maintaining a robust defense budget of at least 4 percent of GDP for five to 10 years.

The military is in a vital phase of mandatory recapitalization.

Under current and future budget projections, the services are scheduled to field new platforms that will anchor U.S. security for the next generation. These include the Army's Future Combat Systems, a platform that will allow our military to be more effective while putting fewer soldiers in danger.

America can afford the needed upgrades. But we aren't making the commitment. The 3.9 percent of GDP we now spend on the core defense budget is far lower than during the Cold War and almost a full percentage point below defense spending in 1950. The defense budget is expected to drop even further to less than 3.2 percent of GDP by 2012.

People here and around the world count on a strong U.S. military for their security. We can't afford any more North Korean-style disasters. Our leaders should agree to spend at least "4 percent for Freedom" each year to ensure that our forces remain capable and ready.

Kim Holmes is vice president for foreign policy and Mackenzie Eaglen is senior policy analyst for national security at The Heritage Foundation.