By VINEYARD HAVEN, Mass. - President Barack Obama will address the nation from the Oval Office and visit troops at Fort Bliss, Texas, on Tuesday to mark the end of U.S. combat operations in Iraq.. Press Secretary Robert Gibbs announced the dual commemoration in a statement and Twitter post yesterday.. It will be the second Obama speech from the Oval Office. He first spoke from the presidential office on June 15 to address the nation about the Gulf oil spill.. Obama will make his second back-to-school speech to the nation's students Sept. 14 at a time to be announced. He wants to encourage them to "study hard, stay in school and take responsibility for their education," the White House said.