sentences:  Lincoln appointed General John C. Frémont to ensure Union control of the area, but Frémont alienated many in the state by declaring martial law and issuing a proclamation freeing slaves that belonged to rebels.Lincoln removed Frémont and reversed the order, but Missouri emerged as the most problematic of the border states for Lincoln.After the defeat at the First Battle of Bull Run, Lincoln summoned Major General George B. McClellan to replace McDowell.