Map of oregon for Later, he also supported the Kansas-Nebraska Act, which allowed the residents of those territories to determine their admission to the Union as slave or free states. This was seen as a betrayal of the Missouri Compromise by permitting Northern territories to become slave states. It resulted in a bloody border war as both sides fought to control Kansas. Pierce also pursued an aggressive foreign policy to expand slave territories. A secret proposal advocating the taking of Cuba by force, made by James BUCHANAN, the minister to Britain, became public. An embarrassed Pierce had to repudiate the document and forego all attempts to acquire Cuba or any other territories. Pierce’s only successful territorial acquisition was the 1853 Gadsden Purchase, encompassing the southern parts of present-day Arizona and New Mexico. Map of oregon 2016.