In his position as Assistant Solicitor and then as Solicitor in the State Department, Clark was often confronted with critical issues of international consequence. For example, when the Mexican Revolution erupted in 1911, he was called upon to make crucial decisions and recommend courses of action to the secretary of state and Howard Taft. Of particular concern to Clark was the plight of the Latter-day Saints who lived in the Mexican colonies and were often caught in the middle of the conflict and whose presence in Mexico was resented by the revolutionaries.