The U.S. wars in Iraq and Afghanistan have been declared officially over, but America has barely begun to pay the bill, says a new study. That could make defending the nation and paying the government's bills even tougher to do in the future. [PHOTO: The 10th Anniversary of the Iraq War] The Iraq and Afghanistan wars will together cost $4 to $6 trillion, according a new study from Harvard University's Kennedy School. A large share of those bills has yet to be paid: the study finds that the U.S. has spent around $2 trillion thus far on the two controversial wars, and that growing commitments to spending on military personnel and veterans will drive much of the spending in the decades to come. The study notes that the Veterans' Affairs budget has tripled since the start of the wars. "Assuming this pattern continues, there will be a much smaller amount of an already-shrinking defense budget available for core military functions," writes Linda Bilmes, senior lecturer in public policy at Harvard and the study's author. Bilmes has been studying the costs of the two wars for years, and she says that the estimates of the total cost continue to climb as the cost of continuing care for veterans mounts. "What has happened is the number of injuries and the number of claims and the complexity of claims...in these conflicts has been much higher than in previous wars," she says. She notes that after Vietnam, veterans averaged around two and a half to three conditions per claim, whereas veterans now have over eight conditions per claim. Read more..