CAMP LEJEUNE, N.C. (AP) President Barack Obama consigned the Iraq war to history Friday, declaring he will end combat operations within 18 months and open a new era of diplomacy in the Middle East. "Let me say this as plainly as I can: By August 31, 2010, our combat mission in Iraq will end," Obama told Marines who are about to deploy by the thousands to the other war front, Afghanistan. Even so, Obama will leave the bulk of troops in place this year, contrary to hopes of Democratic leaders for a speedier pullout. And after combat forces withdraw, 35,000 to 50,000 will stay behind for an additional year and half of support and counterterrorism duties. Just six weeks into office, Obama used blunt terms and a cast-in-stone promise to write the last chapter of a war that began six years ago. It has cost more in lives, money and national stamina than ever envisioned. Like Dwight Eisenhower and Richard Nixon before him, Obama came into office with an inherited war he pledged to end without delay. Eisenhower did, in Korea. Nixon didnt, in Vietnam. Obama says he will. "Iraqs future is now its own responsibility," Obama said. Defense Secretary Robert Gates and Adm. Mike Mullen, chairman of the Joint Chiefs of Staff, flanked Obama during the announcement. It was a symbolic statement that top military advisers are on board with a strategy some had openly questioned before Obamas inauguration. More than five years have passed since Bush declared the end of major combat operations in Iraq, a statement that proved false as sectarian violence brought Iraq to the brink of disaster. Obama did not claim a mission accomplished. Instead, he suggested America accomplished the mission as best it could. "What we will not do is let the pursuit of the perfect stand in the way of achievable goals," he said. "We cannot rid Iraq of all who oppose America or sympathize with our adversaries. We cannot police Iraqs streets until they are completely safe, nor stay until Iraqs union is perfected." He said: "Americas men and women in uniform have fought block by block, province by province, year after year, to give the Iraqis this chance to choose a better future. Now, we must ask the Iraqi people to seize it." Obamas promise to pull home the last of the U.S. troops by the end of 2011 is in accord with a deal that Iraqis signed with former President George W. Bush. Meantime, Obama is accelerating the end of the war by withdrawing roughly 100,000 troops by the summer of 2010. Obama was moving to fulfill in large measure the defining promise of his campaign to end combat operations within 16 months of taking office. Hes doing it in 19 months instead, and the drawdown will be backloaded to provide security for Iraqi elections late this year. More than 4,250 Americans have been killed in Iraq, a costly, unpopular enterprise at home that Obama criticized when support for the invasion was strong and few other politicians dared stand against it. He applauded the armed forces for its successes in Iraq, where U.S. deaths and violence in many parts of the country are significantly down. He never credited Bushs buildup of troops in 2007 as contributing to those improvements. In another break from Bush, Obama promised "comprehensive American engagement" with nations across the Middle East, noting Iran and Syria in particular. The U.S. has long had a diplomatic frost with both countries over their support for militant groups, among other matters. But they hold great sway in the region, and Obama sees a diplomatic opportunity. Obama called Bush shortly before he gave his speech to brief him on his plans. White House press secretary Robert Gibbs called the chat brief and straightforward. In his speech, Obama said to the military members: "We will leave the Iraqi people with a hard-earned opportunity to live a better life. That is your achievement. That is the prospect that you have made possible." As Obama spoke, the camouflage-clad Marines seemed to be taking a measure of the man. They politely applauded their new commander in chief at times, and grew more boisterous when he promised to raise their pay and provide more help for their families. The president also told the Iraqi people they will not be forgotten. "Our nations have known difficult times together," he said. "But ours is a bond forged by shared bloodshed, and countless friendships among our people. Yet he acknowledged violence will remain "a part of life" and daunting problems include political instability, displaced citizens and the stress of declining oil revenues. Obama said U.S. must end the war, both for the future of Iraq and to allow the U.S. to refocus its attention more firmly on Afghanistan. Reaction came from everywhere. In Iraq, where several TV stations showed Obamas speech live, some citizens applauded the ironclad withdrawal plan while others questioned whether Iraq could defend itself alone. On Capitol Hill, Democratic leaders remained cool to the suggestion that tens of thousands of troops would remain. House Speaker Nancy Pelosi, D-Calif., said his announcement was good news because it meant an end to the war, but she cautioned that the troops left behind must have a "clearly defined" mission. Obama succeeded in winning over most Republicans, who initially dismissed the timeline as arbitrary. Sen. John McCain, who lost the presidency to Obama, said he supported the plan. "Let us have no crisis of confidence now," he told his colleagues on the Senate floor Friday. "Instead, let us welcome home our fighting men and women not just thanking them for serving in Iraq, but congratulating them on bringing us to victory there." The president who voted against the war as senator and ran against in his upstart White House bid said the Iraq conflict is one huge, painful lesson. Admonishing the Bush era, Obama said the United States must no longer go to war without clearly defined goals. He said it must communicate the costs of war clearly, use diplomacy as well as military might, not go it alone in security. Said Obama to the men and women in uniform before him: "I promise you that I will only send you into harms way when it is absolutely necessary."