``It was something that tore the community apart,'' said Armstrong, now a Loose Juice vendor on State Street. ``After the bombing, people stood back and took a look at the violence on both sides.''

The bomb went off at 3:42 a.m. on a Sunday in August 1970, killing a physics researcher and damaging 26 buildings.

Echoes of the blast were heard in Belleville, 30 miles from the scene of the explosion. Pieces of the stolen 1967 Ford Falcon Deluxe Club Wagon that had held the bomb were found on top of an eight-story building three blocks away.

The bomb's target -- the Army Math Research Center -- stood barely touched.

Many say the bombing was the culmination of an intense period of student activism and violence, of flag-cuttings, beatings and bombings in Madison.

Looking back now, on the 20th anniversary of the fall of Saigon, few tangible signs of this turbulent period remain.

The vast network of underground newspapers is gone. Countless anti-war groups have de-mobilized. Broken shop windows have been replaced.

Except for a life-sized diorama in the War Veterans Museum on the Capitol Square and an archive of yellowing clips and photos housed in the State Historical Society Museum, nothing is left but memories.

``There's no question that it changed the campus in significant ways,'' said Paul Ginsberg, dean of students at the UW-Madison from 1970 until 1987. ``The Vietnam War -- probably more than any other issue -- brought this community together.''

In his mind's eye, Ginsberg can still see then-UW System President Fred Harvey Harrington and Chancellor Edwin Young crying atop Bascom Hill after the bombing. ``I remember that so vividly,'' he said. ``It took everyone by surprise.''

The period from 1965 until 1970 was a learning period, as UW administrators and police grappled with the ever-mounting anti-war movement.

``No one knew what to do,'' said Edwin Young, who took the post as UW chancellor in 1968. ``It was a very mixed-up situation. Some people were pacifists. Others thought, `Now let's have a revolution.' ''

``Our first reaction was to draw the wagons around,'' said Ginsberg, who heralded this time as a rite-of-passage within the university community. ``We realized we couldn't do that. We had to reach out and talk more.''

Robben Fleming, UW-Madison chancellor from 1964 to 1967, took those words to heart. On one occasion, he wrote out a personal check for $1,155 and bailed 11 anti-war demonstrators out of jail.

The 11 students had been arrested on disorderly conduct charges earlier that afternoon for failing to obey University Police orders to leave the Electrical Engineering Building on Randall Avenue.

``I did it because I don't believe that the university and the students should settle their differences by the arrest pattern,'' Fleming told a meeting of nearly 600 students later that night in February 1967.

After all, Fleming said in an interview last week, those students could not have given their pitch to the student body if they were in jail.

Ironically, Fleming was only reimbursed for half of the bail money. Some of the students, he said, decided to keep it for themselves.

Although the anti-war years were trying times for UW administrators, Ginsberg said some aspects still make him smile. ``It always seemed like the anti-war protests went from noon on Monday until noon on Friday,'' he said. ''It's almost as if everyone understood that we needed a break.''

As a result, many appointments were scheduled during the dinner hour and weekends when the campus was relatively quiet, he said. Then, later in the evening, activity would begin again.

The anti-war protests and rallies sparked unrest on the campus. The University Police bolstered their ranks with the Madison police, then Dane County sheriff's deputies. Officers began to work 12-hour shifts instead of eight.

``We were caught unrehearsed and unprepared,'' said Chief Ralph Hanson, who became university protection and security director in 1965. ``We had not experienced violence on the campus up until 1967 when the Dow Chemical recruiters came to campus.''

Several officers and protesters were hurt in confrontations. One officer, Hanson said, had windpipe damage after being kicked during the protests against Dow, a defense contractor, at the Commerce Building.

Armstrong remembers his roommate being dragged away from the Dow protest, beaten and bloody. ``All the cops went to the hospital,'' he said. ``All the students who were clubbed took care of themselves.''

After a while, Hanson said, there was nothing to do but call in the National Guard. It was 1968. The war in Vietnam had escalated and so had the anti-war activity in Madison.

``We were just about bent to the limits,'' Hanson said. ``We were glad to have the National Guard there. Without them, it would have been hard to keep the campus open.''

Ginsberg remembers when the National Guardsmen stood their posts, bayonets drawn, in front of the old Education Building alongside Bascom Hill. ``It was truly an armed community,'' he said.

Buildings were trashed. Many of the shop windows on State Street had been broken so many times that storeowners just boarded them up and waited for the war to end before making permanent repairs.

Although the bombing of Sterling Hall did not bring an end to the Vietnam War, it signaled an end to much of the anti-war movement.

Eventually, everything returned to normal in Madison, a city that just a decade earlier had been named by Life magazine as one of the best places to live in the nation.

``In the long run, it didn't have much of an impact,'' said George Mosse, a retired UW-Madison history professor, about the Vietnam War. ``What changed? Nothing much.''

Although no physical marks of the Vietnam War era remain, people like Karl Armstrong, who remember the Dow Chemical protest, underground newspapers hawked by the Capitol and shop windows boarded up along State Street, argue that the Vietnam War era left an indelible mark on Madison.