We're told that history repeats itself. Actually, it's people who do that. They repeat their mistakes all the time. That's the real human constant in history. And Washington may be about to give us another history lesson: repeating the gravest misjudgments of the Vietnam War.

When Congress voted to abandon our allies in South Vietnam in 1975, lawmakers patted themselves on the back, arguing that they had made the nation better by walking away from a bad war. Nothing was further from the truth.

The world became more dangerous after America quit Vietnam. Emboldened by the U.S. withdrawal, the Soviets became more aggressive. They embarked on an unprecedented build-up of military force.

The Kremlin directed a worldwide campaign of insurgencies from Latin America to Africa. It even dabbled in support for transnational terrorism. A decade later, the United States had lost the respect of its allies and found itself mired in "brush fire" wars around the world. Many questioned whether the American Age had come to an inglorious end.

Worst of all, Washington virtually abandoned the men and women in uniform. An exhausted military faced an uncertain future. It had skipped a generation of modernization to help pay for the war.

Equipment was worn out after years of jungle combat, while the armed services had to make the difficult transformation from a draft military to an all-volunteer force; meanwhile, politicians took a peace dividend and cut military spending.

By the end of the 1970s, the Pentagon had what Gen. Edward "Shy" Meyer famously called a "hollow" force. On paper there were plenty of troops, he told a congressional committee, but few were prepared for combat. The Pentagon lacked sufficient funds to maintain a trained and ready force, pay for current operations, and modernize the military.

Congress was shocked. But it shouldn't have been.

Three factors contributed to military unpreparedeness. The first was a general disillusionment with the utility of military power. Indeed, many took the lesson of Vietnam to be that the use of armed force created more problems than it solved. A weak military would mean America would be less likely to get into future troubles. Antipathy became a substitute for strategy.

Second, there was a general malaise over the economy. Since Washington didn't want to spend money on the military anyway, framing every fiscal debate as a case of "guns vs. butter" became an easy argument. A dollar spent on the Pentagon was a dollar wasted -- a dollar that instead could have built schools and fixed bridges.

Third, Washington became complacent about threats. Although the Soviet Union had fielded the greatest military machine in human history, the United States had survived three decades of the Cold War and suffered a humiliating defeat in Vietnam -- and the nation was still standing.

It was better, Washington argued, just to live with the evil around us than try to fight back. Threat assessment became making sure our appreciation of the enemy matched the meager defense budgets passed by Congress. Hope became a method, as policymakers simply ignored the dangers too expensive to address.

Rather than spend money on defending ourselves, the thinking went, all we needed were smarter, more honest and compassionate leaders who would tame the world with their sincerity.

These were convenient, convincing and comforting arguments to cut military spending. They were also just wrong. The U.S. economy worsened, and the world became deadlier.

Now we're hearing the same arguments all over again. The answer to all our ills is "end this war." Of course, ending wars won't solve irresponsible tax-and-spend fiscal policies, rebuild the military or restore global confidence in American leadership.

And that's assuming we could just "end" wars -- and you can't. You can lose, quit or win wars ... but you cannot end them simply by walking away. Wars have two sides and the enemy, as the saying goes, "gets a vote." This is the real lesson of Vietnam.

As we saw in the 1980s, there is another way to face adversity. Americans rediscovered that they lived in a resilient and powerful nation that had the means to rebuild the military, stand tall in the struggle against an eternal enemy, and re-energize the economy.

Rather than repeat the infamous "crisis of confidence" of the 1970s, America should stand tall. Win the Long War. Adopt responsible pro-growth policies that will allow the country to prosper and Washington to provide for the common defense.

Let's show that we've finally learned the right lesson.

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