On his first working day as acting defense secretary, Pat Shanahan made clear that his focus is on China.The former Boeing executive, who moved up from the No. 2 job after Pentagon chief Jim Mattis left Monday, gathered civilian leaders of the military services and other top civilian officials at the Defense Department on Wednesday before going to the White House for a Cabinet meeting.A defense official said Shanahan told the Pentagon gathering that he is focused on the strategy as developed and put in place under Mattis. It emphasizes the importance of great power competition with Russia and China, after America’s many years of fighting insurgent wars in the Middle East.In that context, Shanahan said the Pentagon leaders should remember, “China, China, China,” according to the official, who was not authorized to publicly discuss internal defense meetings and spoke on condition of anonymity. The Trump administration has had a rocky relationship with China. Like the Obama administration, President Donald Trump’s government is concerned by what it calls China’s militarization of disputed areas in the South China Sea and by its advances in certain high-tech weaponry.With Shanahan moving up from deputy secretary to acting secretary, at least temporarily, the Pentagon’s budget chief, David Norquist, has been chosen to fill in as the deputy, according to Pentagon spokesman Tom Crosson. As acting secretary, Shanahan has all the authorities of a permanent secretary. It’s unclear whether Trump will nominate Shanahan as Mattis’ successor or will chose someone else. Shanahan had been the deputy secretary since July 2017. He spent his entire career with the Boeing Co. and has no prior government experience.Mattis, a retired Marine general, submitted his resignation on Dec. 20 after a series of policy disagreements with Trump, including the president’s decision to withdraw troops from Syria. Mattis said he would stay until the end of February, but on Dec. 23 Trump announced that Shanahan would take over Jan. 1, speeding up Mattis’ departure.Shanahan, a native of Washington state, had worked for Boeing since 1986. His views on strategic issues such as U.S. alliances and the wars in Afghanistan and Syria are largely unknown to the public. During his Senate confirmation hearing in June 2017, Shanahan drew the ire of Sen. John McCain, R-Ariz., for equivocating on whether he favored providing defensive weaponry to Ukraine in response to Russian military intervention.Shanahan holds a bachelor of science degree in mechanical engineering from the University of Washington and two advanced degrees from the Massachusetts Institute of Technology.It is rare for the Pentagon to be run by an acting secretary. The last was William H. Taft, who served in that capacity for about 60 days in 1989 after President George H.W. Bush’s initial choice to be defense secretary, John Tower, became mired in controversy and ultimately failed to be confirmed by the Senate. Dick Cheney, the future vice president under President George W. Bush, then was nominated and confirmed.