Dierkes was born on February 10, 1905 in Cincinnati, Ohio. He attended Brown University and subsequently went to work as an economist for the United States Department of State. In 1941 he joined the Red Cross and served in the Britain duringWorld War II. There he met director John Huston who recommended that he try Hollywood after the war. Instead, Dierkes went to work for the U.S. Treasury Department which coincidentally sent him to Hollywood to function as technical advisor for the film To the Ends of the Earth (1948). Because of his appearance and very tall frame (6 feet, 6 inches), Dierkes enjoyed a long career as a character actor, often portraying villains or soldiers. In the 1953 film Shane, Dierkes portrays villain Morgan Ryker, who is the last man shot by the title character, Shane, in the final bar room shootout. One of his more memorable scenes is in the 1960 film, The Alamo. Dierkes portrays a Tennessean named Jocko, who is torn between leaving before the attack to care for his blind wife, or staying to support the Texans cause. Understanding that if Jocko stays to fight she will likely be widowed, Jockos wife coaxes him to stay and defend the fort, despite her disability.