Since the Second World War. Americans have been reared to hate aggression and indiscriminate killing. First the Nazis and then the Communists, we were told, were slaughterers and butchers on a vast scale, and the mass murder which characterized both of those political systems would soon characterize our system unless we kept up our guard continuously.

As the Vietnam war escalated and the body counts from Vietnam continued to mount, students, and others, began to apply this moral imperative against genocide against their own government. Even if the Vietnamese dead were all Communist automatons bent on subverting liberty, and even if the American cause was initially just, the extent of the killing, the mounds of the dead, indicated that the government was pursuing a policy of moral obscenity. No political goals were worth such a toll in lives.

Some people objected merely on grounds of inhumanity, while others protested the choice of targets itself. Many began to support, in varying degrees, the North Vietnamese National Liberation Front. But, in either case, for every activist who had come this far, the basis for a firm and lasting alliance was laid. The most hardened NLF supporter and the people who pasted white doves and peace symbols on their windshields had one goal in common--the killing must stop.

This aversion to mass murder of any sort, which grew with each year of bombing, napalming and free-fire zones, explains why a growing number of people, eventually including a majority of America's population, called for withdrawal from Vietnam. The continuing carnage sickened even those on the moderate right, and the unity against the killing gradually broadened.

Among students, however, who had access to greater information about the war and more time to ponder it, questions arose about the unseen enemy. In the face of a nearly total onslaught by the greatest military power in the world, why did these people continue fighting? Who were these Vietnamese, and why did they rebuild bridges with their bare hands and go into battle against an enemy that was vastly superior in the weapons of modern war? Why did they troop down the Ho Chi Minh trail, year after year, to face almost certain annihilation?

As our knowledge of the NLF and of North Vietnam grew, our political support for them also expanded. No longer was the killing itself our only reason for fighting against the war. A new dimension of hatred for the American government surged up in us. No longer were the actions of the U.S. government criminal merely because they unleased indiscriminate violence against a smaller nation. Now, we saw those actions as criminal because the destruction was intended to annihilate a people who were striving against almost insuperable odds to achieve some measure of dignity and control over their own lives--objectives Americans have traditionally championed.

Vietnam became for us a symbol, proof that socialism could work, that people could master their own destiny. The Vietnamese revolutionaries seemed almost superhuman, courageous and cooperative. Socialist Men and Women in the rice field and the high plateaus, calmly firing rifles skyward as American divebombers screamed down to engulf them in flaming destruction. Vietnam showed us that might can never subdue justice, that a people striving together to be free cannot be stopped short of genocide.

So we supported the National Liberation Front. We carried their flags, we honored their heroes, some of us went so far as to see ourselves fighting for them in the streets of America, a fifth column behind enemy lines. We awaited Vietnam's inevitable victory.

FORTUNATELY, the growing support for the NLF did not force radicals into tactics markedly different than those of the liberals who fought against the war on loftier, more abstract moral grounds. The goal for both groups was the same: an immediate end to American military involvement in Indochina. The liberals wanted the killing to stop; the radicals wanted the killing to stop and the NLF to win.

The radicals, of course, were always more strenuous in their opposition to the war, but their participation in trashing demonstrations one day did not prevent them from washing off the tear gas and joining a peaceful rally the next. The antiwar movement was always characterized by several levels of participation: prospective liberal law students could avoid arrest by not attending militant actions and still contribute meaningfully to ending the war by joining the peaceful waves of people who clogged the streets in quiet and orderly marches.

Because the goal was the same, the difference in tactics was usually not broad enough to destroy the radical-liberal coalition. The two groups might have disagreed about the reasons for the war, the structure of American society, the ultimate vision for the just society, but on the central issue of the day they were in agreement--the war must stop. Now that the war seems to be over, this bedrock basis for a firm alliance is eroding, and the two groups are crumbling away from each other.

If the Cambodian bombing continues through the summer, the alliance will reform. But if, as is more likely, Watergate and Congress force an end to the aerial genocide in Cambodia, the war, which has united and shaped American campus protests almost since its birth, will have disappeared. Barring another brutal American intervention in the Third World in the immediate future, radicalism on campus will come to a temporary stasis, probing gently for new outlets.

THE NUMBER of confirmed radicals here probably hovers somewhere around 200--perhaps half what it was at the peak of the 1969-70 activism. Though smaller, this number is still large enough to provide the initial spark for successful activist campaigns. Moreover, most of the Harvard left is centralized in the New American Movement, a group which eschews the fanatic factionalism of the most recent incarnation of SDS. Organizationally, the left is stronger than it has been since 1970. NAM conducted a wide range of activities this year, including support for the United Farmworkers lettuce boycott, a petition campaign against Harvard's Faculty hiring policy--which allegedly discriminates against radicals--and, Vietnam-America Friendship Week, a program of antiwar films and teachins about the war.

By past standards, all of these campaigns were well planned in advance, yet all of them failed in varying degrees. The immediate fault lay not with the radicals, but with the lack of response from Harvard's phalanxes of left-liberals, who still make up the bulk of the undergraduate population.

As recently as 1960, a majority of the undergraduates here were Republicans, but the flow of events in the sixties shoved the entire campus quite a few degrees to the left, situating most students at a point on the political spectrum where they could be drawn into support for activist campaigns.