Who is General Benjamin F. Butler from The Fiery Trial: Abraham Lincoln and American Slavery and what is their importance?

General Benjamin F. Butler commanded Union troops at Fortress Monroe. Early in the war, he began to grant asylum to slaves who approached the fort. When questioned by their owners, who demanded their property be released, Butler refused based on the fact their owners were citizens of seceded states..... part of a now foreign country. Butler then noted that as such, they were not entitled to satisfaction under the Fugitive Slave Law. Butler gave asylum to more than forty slaves before word of his actions caused Lincoln to replace him as commander in order to soothe the border states, which in Lincoln's mind were crucial to the preservation of the Union.