This law, which allowed territories to decide the fate of slavery based on popular sovereignty, unintentionally had the effefct of increasing tensions between pro-slavery and antislavery forces as they rushed west and had violent clashes over control territory

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.