For almost three hours last night, the Cambridge City Council laid aside its usual roster of issues--Proposition 2 1/2, zoning, police protection and the rest--and concentrated instead on the threat posed by global nuclear war.

Though they took no formal action, the councilors who spoke were unanimous in their condemnation of a recently-completed Civil Defense report advising Cantabrigians to head for Western Massachusetts in the event of nuclear war.

All the councilors who spoke agreed as well that the city government should play a role in helping to mobilize public opinion against nuclear weapons and for disarmament.

"It has been said that the Cambridge City Council is one of the few local legislative bodies in the world with its own foreign policy," Councilor David Sullivan said. "On issues like this, it is imperative that other local councils develop foreign policies of their own as well," he added.

The councilors, who heard testimony from George Kistiakowsky, Lawrence Professor of Chemistry Emeritus, and Helen Caldicott, chairman of Physicians for Social Responsibility, focused most of their attacks on the report prepared by the state civil defense office which labels Cambridge a "risk area" and outlines plans for its evacuation.

According to the plan, in the event of a nuclear crisis city residents are to drive across the state on Route 2 until they reach Greenfield, Mass., where they will be boarded in schools and other public buildings.

"It is a farce--it is wrong to tell the public that you can survive a nuclear attack if you drive to Greenfield. Graham said. "If you are stuck in traffic, it says you shouldn't leave your car...It says you shouldn't bring alcohol or narcotics. Maybe those are the only things we should bring with us, just to numb our minds," Graham added.

Citing the traffic jams that snarl the Alewife Brook area during a normal rush hour, Graham said. "Cambridge people are not going to get to Greenfield. They're not even going to get to Route 2."

And Kistiakowsky drew applause when he said. "The people escaping along Route 2 will be worse off--their death will be slower, more unpleasant."

"The only route to national safety, security, and welfare is the route of disarmament." Kistiakowsky, who helped build the atom bombs exploded over Japan at the end of World War II, said.

Councilor David Wylie urged the city's civil defense department to end its evacuation planning and instead mobilize public sentiment against nuclear weapons. "The only way you can help is to tell the citizens that the only way out is disarmament," he told Chester Hallice, the city's director of civil defense.

Daniel Forbes, a state civil defense official, said the "peace movement has failed, year after year," and added that the Russians had a similar plan for getting their citizens out of major population centers.

"If we can move our people, we will restore the balance of power." Forbes said, adding that "if we have a good crisis relocation plan, the chances are we'll never have to use it."