After a brief initial assignment at Fort Hood, Clark served in Vietnam as a Rifle Platoon Leader and Company Executive Officer with the 1st Cavalry Division.

He then became the Deputy Chief of Staff for Combat Developments, United States Army Training and Doctrine Command at Fort Monroe.

Because of this and other incidents at Fort Campbell, Clark's promotion to lieutenant general was opposed by groups such as the National Organization for Women[1] and was delayed pending two Executive Sessions by the U.S. Senate Armed Services Committee.

The official Defense Department reports and the Senate Armed Services Committee exonerated Clark of wrongdoing,[2] and he received his promotion in November 2003.

[3] After his tour at Fort Campbell, Clark was assigned as the Deputy Commanding General, Fifth United States Army.