 That summer Garfield suffered from jaundice and significant weight loss . He was forced to return home , where his wife nursed him back to health . While he was home , Garfield 's friends worked to gain him the Republican nomination for Congress , although he refused to politick with the delegates . He returned to military duty that autumn and went to Washington to await his next assignment . During this period of idleness , a rumor of an extra @-@ marital affair caused friction in the Garfield marriage until Lucretia eventually chose to overlook it . Garfield repeatedly received tentative assignments that were quickly withdrawn , to his frustration . In the meantime , he served on the court @-@ martial of Fitz John Porter , a sensational trial in which Porter was tried for his tardiness at the Second Battle of Bull Run . He was convinced of Porter 's guilt , and voted with his fellow generals to convict . The trial lasted almost two months , from November 1862 to January 1863 , and by the end of it , Garfield had at last procured an assignment as Chief of Staff to Major General William S. Rosecrans . 
