It could not have been easy for President Reagan to decide to stick with his policy of not undercutting SALT II, the (unratified) treaty he had done so much to identify as the epitome of bad arms control. His constituents on the right were bound to recall, in outrage, that he had labeled it "fatally flawed." Pentagon civilian chiefs were pressing him hard to scrap the treaty. Soviet violations are both serious and accepted enough to have given him a strong rationale. Yet Mr. Reagan accepted more pragmatic counsel and did the right thing -- in part to boost the Geneva talks. He agreed to keep in force the policy of not undercutting the terms of the unratified agreement and to stay under a key SALT ceiling not by the gimmick of drydocking an old Poseidon sub but by dismantling it outright.

In so doing, Mr. Reagan walked a fine line between hotly contending parts of his administration. In effect, he said to Secretary of State Shultz and other partisans of the "no-undercut" policy: I am giving you five months to show that it will produce comparable Soviet restraint plus a good-faith Soviet approach to the Geneva nuclear and space talks. To Secretary of Defense Weinberger and others who wanted to scrap SALT II, he said: hold on for five months and then you may tell me what additional arms-building steps are an "appropriate and proportionate" response to the military consequences of uncorrected Soviet violations.

This, then, is Mr. Reagan's response to the problems caused by the Soviet compliance record. One need not accept every item in the Reagan bill of particulars to acknowledge that the Russians have violated in different ways important elements of various arms control agreements. So Mr. Reagan had an obligation to show that he was addressing this special question seriously -- and not just to make good on a campaign pledge or to win the American people's trust for further negotiated arms control.

In the process, he has given Secretary Shultz an extremely demanding assignment, one for which he will need a degree of Soviet cooperation that is hard to imagine. In the short space of five months, he is to produce new Soviet restraint on violations -- a sensible demand, though one that entails difficult issues of definition and verification. He is also to produce progress at Geneva. This may be an impossible condition, given the deadlock now prevailing and the difficulty of breaking it soon even if compliance were no issue. In any event, Mr. Reagan has contrived to ensure that November will be a dramatic month.