About 15 Boston-area students and 30 Cubans gathered last night on the steps of Memorial Church to alert the Harvard community to the "nature and gravity of the Soviet threat" The rally concluded a series of area events sponsored by the Harvard Conservative Club and a national bipartisan student organization opposing unilateral disarmament.

The national group, Students for Peace and Security (SPS), which also organized a colloquium yesterday afternoon at Tufts entitled "The Soviet Threat to Global Peace and Democratic Security," believes that peace can only be achieved by "building up American forces to meet the Soviet challenge." Tufts member lan C. Ballon said yesterday.

Chants of Down with Gucci Liberals and "Peace Through Strength" interrupted the nine successive speakers at last night's rally which included representatives of the former Communist Hanoi Government and the Abdala Cuban Movement an anti Castro organization A Soviet emigre warned of the miliaturization of Soviet society, following other speakers' warnings that " it's not too late to get rid of the Soviet regime."

Mark A Sauter '82, a member of the Conservative Club and of SPS mocked "peaceniks" who support unilateral disarmament, and criticized "the naivete of the left."

The Tufts colloquium, attended by more than 200 students, featured Richard Pipes, senior member of the National Security Council and Baird Professor of History, who said that the Soviets are "exacerbating problems, not solving them." He added that the Soviets "the great hawks who have survived the worst bloodbath of history"--have been famed by the Reagan Administration.

SPS, which began organizing four months ago at Tufts, is represented on 15 college campuses nationwide and hopes to become an international organization. Tufts coordinator Fabian Bachrach said yesterday. The bipartisan group has at least five Harvard members, most of whom are Conservative Club members, Sauter said.