"Mission accomplished" is a military phrase associated with completing a mission. It was used controversially by the American military and Republican politicians in reference to the United States' at-the-time-unfinished entanglement in Iraq.
 John McCain
“”NEIL CAVUTO: ... Senator -- after a conflict means after the conflict, and many argue the conflict isn't over. JOHN MCCAIN: Well, then why was there a banner that said 'mission accomplished' on the aircraft carrier? ... the conflict -- the major conflict is over, the regime change has been accomplished...
John McCain denounced the phrase on May 1, 2008, saying:
“”I don't know if you could ever say, quote 'mission accomplished,' as much as you could say 'Americans are out of harm's way.' And that's the key to America's concern — casualties.
 Bush administration
The phrase had earlier been seen on a sign displayed on the USS Abraham Lincoln (sorry, Abe) during a televised address by United States President George W. Bush on May 1, 2003, when he stated that major combat operations in Iraq had "ended."
Conservatives try to defend Bush by saying this had nothing to do with Dubya, and everything to do with the Lincoln Carrier Battle Group, which did accomplish its mission. And for months, the Bush administration denied that it was responsible for the banner, blaming the aircraft carrier crew itself for putting it up.
Since then, White House officials have acknowledged it was their idea. "We put it up. We made the sign," former White House spokesman Ari Fleischer said. "But I think it accurately summed up where we were at the time, mission accomplished...the mission was to topple Saddam Hussein."
 Mission actually accomplished(?)
Bush signed an order to have all troops removed from Iraq by the end of 2011, which President Barack Obama dutifully carried out, much to the dismay of his detractors. Whether or not the original goals of a military intervention in Iraq were realized is still to be determined (unless the goal was to create ISIS).