From 1965 to 1997, he had a distinguished military career in the U.S. Army, with multiple assignments to various parts of the world, retiring as a highly decorated Major General.

[5] After returning to the United States, he continued his career commanding and training military police detachments.

[8] On September 18, 2014, Lenhardt was confirmed to be the Deputy Administrator of the Agency for International Development.

[10] Gayle Smith, President Barack Obama's nominee to be Shah's permanent successor, was confirmed by the Senate on November 30, 2015, and assumed the role of administrator on December 2, 2015.

In the 2024 United States presidential election, Lenhardt endorsed Kamala Harris.