WASHINGTON (TIP): Deputy defense secretary Ashton Carter, known for his deep knowledge of US defense spending and the defense industry, said on Thursday he was stepping down in December after four years in top Pentagon jobs. Defense secretary Chuck Hagel said he “reluctantly accepted” Carter’s decision to leave the post. Carter brought fresh analytical rigor to the job, but also helped reopen lines of communication with the defense industry, said Brett Lambert, who worked closely with Carter before retiring in August as the Pentagon’s head of industrial policy. But Carter’s main legacy was his “unwavering, untiring and overwhelming” commitment to making sure that US troops had the equipment to do their jobs, Lambert told Reuters. Over the years, that meant researching and sending in an array of unusual equipment – from explosive-sniffing dogs to surveillance blimps and mine-resistant trucks that could climb the mountainous roads in Afghanistan. “I truly believe he saved lives over there,” Lambert said. It was unclear who might replace Carter, although several names surfaced late Thursday as possible successors: Navy secretary Ray Mabus, former Air Force secretary Michael Donley and the Pentagon’s former policy chief, Michele Flournoy. Another possible contender might be Linda Hudson, a veteran defense industry executive who has announced plans to retire early next year as chief executive of BAE Systems Inc, the US unit of Britain’s BAE Plc. As deputy defense secretary over the past two years, Carter helped ensure a smooth hand-off from then defense secretary Leon Panetta to Hagel.