In 1977, I was commissioned into one of the worst armies in American history. The United States left Vietnam with a demoralized, poorly trained, ineptly led and over-stretched military.

Over the next decade, however, I participated in a remarkable transition. America abandoned the draft and began fielding a professional, well-equipped, all-volunteer force.

In my 25-year career, I saw the worst of times become the best of times. It is inconceivable that anyone could suggest that America abandon a winning formula. But that, in effect, is what advocates of a new draft are suggesting.

One of the cornerstones of our all-volunteer force is the Reserves -- men and women called to active duty only for training or deployments. Otherwise, they pursue their civilian careers -- part-time soldiers fully committed to serving the nation. When not deployed, the cost of retaining Reserve forces is a fraction of the expense of full-time, active-duty troops. Maintaining a large Reserve, about 47 percent of the total military, allowed the Pentagon to pour more resources into buying new equipment and improving training.

The results speak for themselves. Today, we have the best military on the planet.

Most important, the Reserve force allows for the rapid expansion of force in times of trouble. The War on Terror has presented us with one of those troubled moments. Reserves have been called to serve in numbers unprecedented since World War II. The latest call-up began July 6, when the Army started notifying about 5,600 Americans to get ready to go. They are drawn from a pool of about 100,000 men and women called the Individual Ready Reserve, or IRR.

The IRR makes up a small part of the approximately 1.3 million that make up the military's Reserve. They are individuals who still have an obligation to military service but are not assigned to specific units and do not conduct periodic training. Mostly, they are individuals with special skills now in high demand.

Announcement of the IRR mobilization prompted shrill criticisms that the military is overstretched, as well as ill-considered recommendations to bring back the draft to increase the size of the Army permanently. But we are using our Reserves exactly like we're supposed to -- calling on them when the nation truly needs them.

Yes, calling Reserves to active duty often results in hardship and sacrifice. That is the nature of volunteer service -- a tradition that dates back to the first colonial militias. Volunteer military service is a reminder that citizenship carries both privileges and responsibilities and that in a free society we depend on the people to determine how and when to meet their obligations. In the American tradition, conscription is appropriate only in moments of extreme national crisis, such as World War II, when the nation needed 10 million men in uniform.

A draft today, moreover, likely would be as socially divisive as Vietnam-era conscription. It would result in a less well-trained and more costly military; new conscripts would have to be trained every year to replace those who leave. And it wouldn't provide the critical skills we need -- skills that require long years of training and experience.

Equally wrongheaded are congressional efforts to permanently increase "end-strength," the number of troops the Pentagon is required to have in the active force at the end of each fiscal year. Permanent increases would be extraordinarily expensive and make it harder to modernize and transform the force. The result would resemble the "hollow Army" of the 1970s. Besides, by the time we could ramp up new forces (probably about two years), the need for additional troops in Iraq likely will subside.

The Pentagon has the right answer: relying on the Reserves and extending the tours and service of soldiers for the good of the nation.

The real problem isn't a shortage of troops. It's that our current force isn't structured for today's missions. After all, something's wrong when the armed services can't sustain 150,000 troops in Iraq and Afghanistan with more than 3 million in uniform.

Defense Secretary Donald Rumsfeld is committed to reshaping the force so that America can put more and more of the right kinds of troops in the field -- where we need them and when we need them. Congress should put more of its energies behind supporting the Pentagon's initiatives -- and spend less time trying to revive the draft and saddle the military with forces it can't afford.

James Jay Carafano is a senior research fellow for defense and homeland security at The Heritage Foundation (heritage.org).