Perhaps I can help.
1) We earnestly do not believe that those troops who are dying are doing so in vain or "for no reason," at least as long as we stay and finish the job. Look, the Bush administration overplayed the WMD thing. That's fine, beat them up for that; they took a gamble and lost and deserve it. But the case for war was never a one-legged stool. Don't imagine for a second that a single person on earth believes that WMD alone would have justifed this war. Pakistan has WMD. Russia has WMD. We have WMD. Even other direct threats like Iran and Libya have WMDs or WMD programs. WMD alone did not cause this war. Try this on. Saddam Hussein was a bad person for a host of reasons and could not be allowed to run a pivotal country in the post 9-11 world. That's why we did the war, OK? It's really that simple. The world changed on 9-11 and some threats were previously OK to appease or contain were no longer appeasable or containable. And at the core, in our hearts, we believe that removing Saddam Hussein from Iraq was, is and will be a noble mission.
2) The troops, broadly, do not believe that they are dying for no reason. The anti-war left and its pro-terrorist allies can say that they're for the soldiers all day long; many of them will even be telling the truth as they see it. But the people who are actually in the military, the people who are at risk, overwhelmingly believe in the mission. The soldiers rotating off duty are telling us, when we ask them, that they have fallen in love with the Iraqi people and want them to be as free of the terrorists and criminals and remnant Ba'athists as they now are of Saddam Hussein. They believe that their job is not done, and they want to finish it. Volunteers for return tours are sky-high. Reinlistments are sky-high. It is their earnest belief that the best way to support them is to let them finish their jobs. Read the words of Marine Cpl. Jeffrey Starr, who wrote a letter on his laptop to be delivered to his girlfriend if he were to die on his third tour of duty in Iraq: "I don't regret going, everybody dies but few get to do it for something as important as freedom. It may seem confusing why we are in Iraq, it's not to me. I'm here helping these people, so that they can live the way we live. Not have to worry about tyrants or vicious dictators. To do what they want with their lives. To me that is why I died. Others have died for my freedom, now this is my mark.'"
That is why many of us believe that we can best support the troops, and our country, by finishing the job in Iraq.