The current thrust of US Democratic criticism on Iraq is that Bush has been too soft: he didn't send enough troops in the beginning and now he's too timid with insurgent strongholds. Thomas L. Friedman says there is a Rumsfeld Doctrine: "just enough troops to lose."
This characterization of the Bush team as peaceniks is partially true in a tactical sense. Though their goal is to provoke and use violence in a spectacular way to enhance their power, they are smart enough to know that they have to take some precautions in how they do it.
There are at this point in history only loose, minimal political constraints on the number of foreigners they can kill -- when asked after the 1991 Gulf War how many Iraquis the US had killed, then - Joint Chiefs of Staff Chairman Colin Powell replied "It's really not a number I'm terribly interested in." (Patrick W. Tyler,"Powell Says US Will Stay in Iraq 'For Some Months'," New York Times, March 23, 1991) -- but they do have to avoid sacrificing too many US troops.
Vietnam was a fiasco for the US establishment not just because they lost the war, but also because a substantial portion of the US public rose against it. Its rightly assumed that two major reasons for that rising were the fact that the draft was still in place and the fact that roughly 58,000 US troops were killed (the more than two million Vietnamese dead were a contributing, but less politically important factor). The solution to these problems was to abolish the draft and then to alter tactics, using foreign surrogates and long-range bombing and shelling as substitutes for US ground troops, and trying to henceforth only attack countries and armies that couldn't defend themselves. If US ground troops had to be used, the rule was to get it over with quickly, before activists and those close to the victims had a chance to mobilize.
Now Democrats criticize the Republicans' tactics because the Democrats are out of office, but they will face the same problem if they win: how do you go around staging wars in a political environment where the public has inconveniently decided that they will place a high value on at least one kind of human life -- in this case the lives of US soldiers? It is a fundamental constraint -- and also a fundamental accomplishment of the anti-war movements that began in the '60s.
But imagine if the progress toward civilization continued and the fair-thinking people of today were able to engender an environment in which all human life was valued? That wouldn't and shouldn't abolish war -- sometimes, unfortunately, violence is necessary for self-defense or justice -- but it would make it vastly more difficult for rulers to stage war for insufficient reasons. Imagine if Colin Powell didn't have the luxury of saying he doesn't care, and the political price paid for, say, killing an Iraqui civilian equaled that for losing an American soldier.
Though Bush is vilified by Democrats he has actually killed fewer Iraquis than did Bill Clinton (the Clinton era sanctions killed well in excess of 400,000), but he has dramatized a fact that has prevailed in big powers throughout history: wars and mass killings can be staged for marginal reasons, almost for the hell of it. But that won't work if enough people mobilize and start counting every soul.