KABUL, Afghanistan — An American major general was shot to death Tuesday in one of the bloodiest insider attacks of the long Afghanistan war when a gunman dressed as an Afghan soldier turned on allied troops, wounding about 15 including a German general and two Afghan generals.

The Army identified the American officer as Maj. Gen. Harold J. Greene, a 34-year veteran. An engineer by training, Greene was on his first deployment to a war zone and was involved in preparing Afghan forces for the time when U.S.-coalition troops leave at the end of this year. He was the deputy commanding general, Combined Security Transition Command-Afghanistan.

Greene was the highest-ranked American officer killed in combat in the nation’s post-9/11 wars in Iraq and Afghanistan and the highest-ranked officer killed in combat since 1970 in the Vietnam War.