And now, Mr. President, bring back the draft

All the cruise missiles, B-1 bombers, Trident submarines, laser-guided antitank missiles, and neutron bombs that money can buy will not purchase a down payment on the cost of freedom. They are only the tools. The nation's real investment is in the people who will use the tools to protect what is precious to them.

President Reagan showed great political courage in reversing his campaign promise to eliminate draft registration. The tense Polish situation made the decision easier, but the President must go a step further -- he must reinstitute the draft.

Without a military draft we are walking on a banana peel across an ice field. Smart bombs demand smart soldiers to maintain and operate them. The Army's Black Hawk helicopter has 257 knobs and switches, 135 circuit breakers, 62 displays, and 11.7 square feet of instruments and controls. Pilots need more than the seat of their pants to fly it, let alone use it efficiently.

Since the end of the Vietnam war the all-volunteer force has, for the most part, met its goal of providing the manpower needs of greatly reduced armed forces, but it has not provided a force to defend America adequately. The ''ready reserve,'' the citizen soldiers to whom the nation historically has turned in times of trouble, is 370,000 men short of strength.

Only 10 years ago, millions of Americans took to the streets and millions more who had lost sons and husbands nodded in quiet agreement in opposition to a system that selected some to serve and allowed others to escape service. The Selective Service System was inherently wrong, the argument went, because it chose those who could not afford the sanctuary of the college campus and sent them away to tiptoe through the booby traps and deal with jungle ambushes. The system was unfair because the best and the brightest avoided the ugliness and danger of fighting for their country.

America needs selective service now, because it needs an Army made up of the best and the brightest. We need them to serve in an Army that is increasingly technological. We need smart soldiers, trained by smart noncommissioned officers , led by smart officers. The World War II stereotype of Willie and Joe, the grizzled infantrymen squatting in a muddy foxhole as the image of the ultimate fighting weapon, has been replaced.

The US ranks fifth in the world in standing armies, behind China, the Soviet Union, Vietnam, and India. Although Americans form the major force in NATO and present the chief deterrent to Soviet aggression, according to Jane's ''Armies of the World,'' the manpower shortage in the US Army is a major problem. China has 3.2 million soldiers, the USSR 1.8 million, Vietnam 1 million, and India 950 ,000. The US Army numbers only 750,000.

A return to some form of the military draft might enhance America's credibility as an ally. West German Chancellor Helmut Schmidt has warned that, ''there is a difference between a country that has a military service obligation . . . and a country which has abolished the draft.''

We must have a system that requires the best of its young people to serve. That is not an easy conclusion to reach for a father of draft-susceptible children. The prospect that they, their friends, and other young men and women must give up time from careers or studies is not a pleasant one. The thought that they might have to fight and perhaps even die for their country is chilling. Even more chilling is the thought that someday they might not live in a free country, because we failed to face up to the fact that our force in readiness is not ready and that we did not have the resolve to correct the situation.

In addition to enhancing our military preparedness, we must tell our would-be enemies that we have the resolve to defend ourselves. That message alone might be enough to ensure that we will never again have to march to war.