The analogy between Iraq and Vietnam has mostly been the province of the anti-war side. Opponents of both wars used the same mix of moral and practical considerations, arguing in each case that the American involvement would result in troops being bogged down in a pointless and unwinnable conflict – arguments that have substantially been borne out by the facts.

Last week, George W Bush turned the Vietnam analogy on its head, claiming that the subsequent history of Indochina provided an argument for the continued American presence in Iraq. In doing so, he inadvertently drew attention to a major point at which the analogy breaks down.

Opponents of the Vietnam war argued that the conflict was a civil war within South Vietnam, with a popular uprising against the corrupt US-backed government. We know now that this was completely wrong; the Viet Cong were not a home-grown democratic resistance movement, they were the agents of a Soviet-backed North Vietnamese military invasion.

That fact in turn is critical to understanding the dreadful humanitarian consequences of the communist victory, to which, as Paul Monk points out in today’s Age, many anti-war protesters were callously indifferent.

But in Iraq there is no North Vietnam and no Soviet Union. There is no opposing army waiting to take over when the Americans leave. The terrorists of al-Qa’eda would get a brief boost in prestige, but no material advantage. Without the foreign occupation, Iraq would be left to sort out its own problems, as South Vietnam was not.

As Monk points out, the possible adverse consequences in Iraq – civil war, foreign intervention and a worsening geopolitical position – are precisely the ones that were predicted but did not happen in Vietnam.

Bush’s concern for the victims of communism in Indochina is praiseworthy, although his belief that they would have been helped by an extended American presence is debatable at best.

But dwelling on their plight does nothing to help his case in Iraq.