You aren’t really the U.S. president until you’ve ordered an air strike on somebody, so Barack Obama is certainly president now: two in his first week in office. But now that he has been blooded, can we talk a little about this expanded war he’s planning to fight in Afghanistan?

Does that sound harsh? Well, so is killing people, and all the more so because Obama must know that these remote-controlled Predator strikes usually kill not just the “bad guy”, whoever he is, but also the entire family he has taken shelter with. It also annoys Pakistan, whose territory the United States violated in order to carry out the killings.

It’s not a question of whether the intelligence on which the attacks were based was accurate (although sometimes it isn’t). The question is do these killings actually serve any useful purpose. And the same question applies to the entire U.S. war in Afghanistan.

President Obama may be planning to shut Guantanamo, but the broader concept of a “war on terror” is still alive and well in Washington. Most of the people he has appointed to run his defence and foreign policies believe in it, and there is no sign that he himself questions it. Yet even 15 years ago the notion would have been treated with contempt in every military staff college in the country.

That generation of American officers learned two things from their miserable experience in Vietnam. One was that going halfway around the world to fight a conventional military campaign against an ideology (communism then, Islamism now) was a truly stupid idea.

The other was that no matter how strenuously the other side insists that it is motivated by a world-spanning ideology, its real motives are mostly political and quite local (Vietnamese nationalism then, Iraqi, and Afghan nationalism now).

Alas, that generation of officers has now retired, and the new generation of strategists, civilian as well as military, has to learn these lessons all over again. They are proving to be slow students, and if Obama follows their advice then Afghanistan may well prove to be his Vietnam.

The parallel with Vietnam is not all that far-fetched. Modest numbers of American troops have now been in Afghanistan for seven years, mostly in training roles quite similar to those of the U.S. military “advisers” whom presidents Dwight D. Eisenhower and John F. Kennedy sent to South Vietnam from 1955 to 1963.

The political job of creating a pro-western, anti-Communist state was entrusted to America’s man in Saigon, Ngo Dinh Diem, and the South Vietnamese army had the job of fighting the Communist rebels, the Viet Cong.

Unfortunately, neither Diem nor the South Vietnamese army had much success, and by the early 1960s the Viet Cong were clearly on the road to victory. So Kennedy authorized a group of South Vietnamese generals to overthrow Diem (although he seemed shocked when they killed him).

And Lyndon B. Johnson, who succeeded Kennedy soon afterward, authorized a rapid expansion of the American troop commitment in Vietnam, first to 200,000 by the end of 1965, ultimately to half a million by 1968. The United States took over the war. And then it lost it.

If this sounds eerily familiar, it’s because we are now at a similar juncture in America’s war in Afghanistan. Washington’s man in Kabul, President Hamid Karzai, and the Afghan army he theoretically commands have failed to quell the insurrection, and are visibly losing ground.

So the talk in Washington now is all of replacing Karzai (although it will probably be done via elections, which are easily manipulated in Afghanistan), and the American troop commitment in the country is going up to 60,000. Various American allies also have troops in Afghanistan, just as they did in Vietnam, but it is the U.S. that is taking over the war.

We already know how this story ends. There was not a lot in common between presidents Kennedy and George W. Bush, but they were both ideological crusaders who got the United States mired in foreign wars it could not win and did not need to win. They then bequeathed those wars to presidents who had ambitious reform agendas in domestic politics and little interest or experience in foreign affairs.

That bequest destroyed Johnson, who took the rotten advice of the military and civilian advisers he inherited from Kennedy because there wasn’t much else on offer in Washington at the time. Obama is drifting into the same dangerous waters, and the rotten advice he is getting from strategists who believe in the “war on terror” could do that for him, too.

He has figured out that Iraq was a foolish and unnecessary war, but he has not yet applied the same analysis to Afghanistan. There are two questions he needs to ask himself. First: did Osama bin Laden want the United States to invade Afghanistan in response to 9/11? The answer to that one is, yes, of course he did.

And second: of all the tens of thousands of people whom the United States has killed in Afghanistan and Iraq, would a single one have turned up in the United States to do harm if left unkilled? Answer: probably not. Other people might have turned up in the U.S. with evil intent, but not those guys.

So turning Afghanistan into a second Vietnam is probably the wrong strategy, isn’t it?

Gwynne Dyer’s latest book, Climate Wars, was published recently in Canada by Random House.