Alcohol abuse during the Vietnam War was a significant problem for Australian troops who were supplied with the equivalent of more than five cans of beer per soldier per day during the latter years of the conflict, an official record says.

But some Australian commanders regarded beer as a lesser evil than the heroin and marijuana that gained popularity with allied U.S. troops fighting in the conflict, according to the third and final volume of the official history of the Australian Army in Vietnam, "Fighting to the Finish," which is being published Tuesday.

"A few Australian commanders said the Aussies had a drinking culture and they were safer keeping that under control then allowing them access to what could have been far more damaging," co-author Ashley Ekins told The Associated Press on Monday.

"It was a big problem that every Australian task force commander had to confront," said Ekins, an Australian War Memorial historian.

While Australian troops were barred from drinking during combat operations, binge drinking was a popular form of relaxation when troops returned to bases at Nui Dat and Vung Tau.

In all three cases in which Australian privates murdered superior officers during Australia's decade-long military involvement in Vietnam that ended in 1972, the culprit was drunk, the book says.

When a lieutenant who broke up a party was later murdered by a drunken soldier who threw a grenade into his tent in 1969, another officer in the same tent was so drunk that he slept through the explosion.

"The biggest problem from the man management point of view in Vietnam ... was grog," Col. Max Simkin, commander of the Australian logistics base at Vung Tau from 1969 to 1970, is quoted as saying. The Vung Tau base's average consumption rate at the time of six cans a day was higher than at the Australian headquarters at Nui Dat.

Alcohol was "behind most of discipline problems in Vietnam," Simkin said.

Records cited by the book show that army canteens were supplied with 7.5 million cans of Australian beer in the six months ending in November 1969. With 7,500 Australian troops in Vietnam at the time, that provided a daily average of between five and six cans.

Various Australian commanders tried different methods to curb the excesses. A ration of two cans a day was introduced. Soldiers came back to base after weeks on patrol and drank their accumulated rations in a sitting. Soldiers who stayed behind on base reported that rationing was easily circumvented most days.

Problems attributed to alcohol included fights between soldiers and injuries from vehicle accidents and accidental weapon discharges.

Doctors reported that alcohol abuse was implicated in up to a quarter of all psychiatric cases referred to them.

But drug abuse remained rare. The book cites a 1971 official survey of U.S. servicemen leaving Vietnam that reported two-thirds had experimented with marijuana, a third had tried heroin and a fifth were addicted to drugs.

A total of 60,000 Australian troops served in Vietnam from 1962 until 1972, and around 500 died.

Australia currently has 1,550 troops in Afghanistan, where none is allowed to drink.