What was lincoln’s strategy for keeping the border states in the union?

"The border states during the Civil War were the slave states that didn't leave the Union. These states included Delaware, Kentucky, Maryland, and Missouri. ... Kentucky - President Abraham Lincoln considered Kentucky's loyalty to the Union as an important factor in the Union winning the Civil War."  - Ducksters.com

the monroe doctrine is the best known u.s. policy toward the western hemisphere. buried in a routine annual message delivered to congress by president james monroe in december 1823, the doctrine warns european nations that the united states would not tolerate further colonization or puppet monarchs.

i would also go with d hope u get it right