Americans now agree on the need to renew and revitalize our military forces. Improvements are in process for our strategic nuclear forces, the land, sea and air units prepared for conventional continental conflict and the Rapid Deployment Force being built for medium-scale intervention missions. But examined on the scale of which Americans will see live combat, those most likely to fight deserve first priority.

In the world President Reagan looks out on, American diplomats are threatened, terrorists of all descriptions are at large, and the conviction persists that America may become more muscular but lacks the wit or will to act effectively. Cuban, East German and other Soviet proxies proliferate in Africa, the Middle East and Central America, and ideologues such as Qaddafi, Khomeini and Castro plot to isolate the United States by subverting its allies. The contrast between the disastrous Iranian mission and successful comparable actions in recent years by Israel, Germany, Britain and France suggests that other groups will believe they can challenge American "superpower" with impunity, humble American citizens and overthrow America's allies.

Small unit elite forces and personnel will almost certainly see live action against these attacks. Even President Carter overcame his reluctance to see Americans in combat and dispatched the hostage rescue mission to Iran and an advisory team to El Salvador's internal war. President Reagan and Secretary of State Alexander Haig have announced that the United States will not react softly to terrorism.

But these forces are poorly prepared to respond. Our elite units are scattered through the military services without central command -- Special Forces in the Army, SEALS in the Navy, commando units in the Air Force, recon units in the Marines, area specialists and linguists in intelligence, advisory and training units. In the Iranian mission, the Pentagon produced a force and command structure with bureaucratic deference to all the different uniforms, but at a cost to cohesion and decision. Our military's tradition of preparing for great wars causes disdain for the extra costs in leadership and resources demanded by elite forces, which must be subtracted from the mass units. Institutional distinctions between the military and civilians deprive our advisory temas of the more subtle political and psychological capabilities of the Foreign Service and our information and intelligence services.

A simple alternative is available. An elite staff must be formed, reporting to the chairman of the Joint Chiefs of Staff, but not to the coordinating labyrinth of the component chiefs or the joint staff. This staff must organize, plan for and establish ready logistics and other support for a unit of several hundreds -- volunteers from the military services and appropriate civilian agencies such as the Foreign Service and the CIA. The unit should be put in a single training area to form teams and relentlessly train and practice for hostage rescue, ship and aircraft recapture, POW release and terrorist capture, with its own organic light aircraft, helicopter and maritime capabilities.

The closest of links must be maintained with intelligence agencies so that the unit is kept currently informed of potential threats and can be dispatched the afternoon the president orders. Unit personnel should be formed into advisory teams for assignment to countries facing the challenges of terrorism, subversion and turmoil, needing fully integrated political, psychological, paramilitary and police tactics and techniques rather than conventional military advice alone. Rotation out of the unit after a three-to-five year tour should be required to keep its personnel fresh and be rewarded by choice assignments ahead of others who chose less challenging career tracks.

With the near-certainty that actions of this sort are ahead, even if our improved regular military forces deter higher orders of violence, we should ensure that the courage of the volunteers who will fight these battles is matched by the forethought of their leaders in preparing and organizing them for combat.