Britain and Argentina stick to their guns; For US, Soviet strategists, a proving ground for weapons

The battle in the South Atlantic thus far confirms the strengths and weaknesses of Argentine and British forces.

But engagements over the Falklands also are providing an important laboratory for weapons and strategies that until now have been largely untested.

Military planners in the Pentagon and the Kremlin are learning lessons that will be valuable for decades to come -- lessons that could alter future conflicts.

Britain has struck its strongest blow with one of its modern nuclear-powered submarines. Argentina has fought back most effectively with its modern, missile-equipped, high-performance aircraft.

The exchange in what is essentially a sea battle raises anew questions about the vulnerability of surface naval forces in an age of long-range, highly sophisticated airborne weapons and submarines whose greatest strength is stealth.

Does the Falklands experience support or call into question the current US plan to mount a 600-ship navy designed not only to protect sea lanes, but to project power into any part of the world?

The debate between US Navy Secretary John F. Lehman Jr. (the most forceful of the service secretaries) and his critics no doubt will continue. Only now, it will be argued with better, battle-tested data.

The destroyer Sheffield was one of Britain's newest and most sophisticated. Armed with modern radar, sonar, guns, and missiles, it was designed to defend a task force against air attack.

Yet it was a single missile from a lone Argentine jet fighter that destroyed the Sheffield.

The missile in this case was a French-made Exocet, which is part of both countries' armories. The Exocet can be air-launched from more than 20 miles away , is self-propelled, and can reach its target with radar-guided accuracy at so low an altitude that stopping it after launch is extremely difficult.

Both the US and the Soviet Union have and are developing missiles of this type as well as longer-range conventional cruise missiles to be used against ships.

What is lacking from the British task force is a strong fighter-interceptor able to counter air attack far away from the fleet. Pentagon naval experts say this argues for larger aircraft carriers with scores of top-line fighters like the F-14 Tomcat that currently is part of the US fleet.

Although they have not gone unscathed, Britain's Harrier jumpjets also have proved their combat worth.

They have been used in successful ground attack against Argentine airfields on the Falklands, and have utilized their extreme maneuverability to down at least one opposing fighter.

The US Marines now have five squadrons flying 61 V/STOL (vertical/short takeoff and landing) Harriers, and the Reagan administration is asking for more to replace less capable marine aircraft. At the moment, the Soviet Union has 45 similar V/STOL jets (the Yak-36 Forger) aboard its carriers.

Both sides are keenly interested in how well the British Harriers do.

Some US defense experts argue that there ought to be greater emphasis on V/STOL aircraft and less on jets that require long runways or big carriers with catapults.

The ability of a modern British submarine to get close to and sink an Argentine cruiser also highlights the effectiveness of undersea forces and the means of defending against them.

Argentina does not have the strong antisubmarine capability of the British, who destroyed an Argentine sub when it retook South Georgia Island.

The US does have a superior antisubmarine capability, but it is outnumbered by the Soviets in attack subs by more than three to one.

Some military experts in Congress say the US should put more of its defense resources into attack subs and less into surface vessels. The South Atlantic sea battle may prove them right.