Impact of the Dred Scott Decision on Civil War Tensions

During the 1850s, the debate over the expansion of slavery into newly acquired territories intensified, leading to a series of legislative compromises and violent confrontations. Some key events during this period included the passage of the Kansas-Nebraska Act, which allowed settlers in those territories to determine the legality of slavery through popular sovereignty. This act ignited violent clashes known as 'Bleeding Kansas' and contributed to the rising tensions between pro-slavery and anti-slavery factions.

Which of the following events or developments most directly resulted in the escalation of conflict between pro-slavery and anti-slavery factions during this period?