a close friend and political ally of abraham lincoln, mcclernand was given permission to recruit a force to conduct an operation against vicksburg, mississippi, which would rival the effort of grant, his department commander. grant was able to neutralize mcclernand's independent effort after it conducted an expedition to win the battle of arkansas post, and mcclernand became the senior corps commander in grant's army for the vicksburg campaign in 1863. during the siege of vicksburg, grant relieved mcclernand of his command by citing his intemperate and unauthorized communication with the press, finally putting an end to a rivalry that had caused grant discomfort since the beginning of the war. mcclernand left the army in 1864 and served as a judge and a politician in the postbellum era.