Brownlee became the 27th Under Secretary of the Army on 14 November 2001, following his nomination by President George W. Bush and confirmation by the United States Senate. From 10 May 2003 until 19 November 2004, he served as the Acting Secretary of the Army. As Under Secretary, Brownlee assisted the Secretary in fulfilling statutory responsibilities for recruiting, organizing, supplying, equipping, training and mobilizing the United States Army and managing its $98.5 billion annual budget and more than 1.3 million active duty, Army National Guard, Army Reserve and civilian personnel.