A Tank By Any Other Name ...

MOST people would know a tank when they saw one. Or would they?

One nettling problem for negotiators trying to cut nonnuclear forces in Europe is that East and West use different rules for counting and classifying weapons, including tanks. This explains some of the discrepancies between numbers the two sides toss around when talking about who has the conventional edge.

The Soviets, for instance, lump all tanks into one category, no matter how lightly armored. The West, meanwhile, only counts heavily armored main battle tanks in its estimates.

``We have to sit down and ask ourselves: `What is a tank?''' says one military expert working behind the scenes at the Vienna negotiations.

Take, for example, the French-built AMX-13, classified by the West as a ``light tank,'' and therefore not included in the NATO tally.

It's possible, say analysts, that the Warsaw Pact included light tanks in its estimates of Western tank strength. (See chart, Page 3.) That would explain why the East's figures pump up the number of tanks in the West - as well as their own.

The US-made M-109 Howitzer is technically a piece of ``self-propelled artillery.'' But most people - and not just novices - would call it a tank if shown a picture of it.

Indeed, that's what happened recently when US officials in Vienna put together a pamphlet about the conventional arms talks. One embassy official, who had served in the military, pointed out what he thought was a printing error, since the M-109 was pictured under the heading ``artillery,'' rather than ``tanks.''

``Ninety-five percent of civilians would make the same mistake,'' says the expert. But in this case, he adds, the Soviets don't call it a tank either.