 The men had been captured by a large force composed mostly of German volunteers during an unsuccessful attempt by the pro-southerners to seize the Federal arsenal in St. Louis.The prisoners were guarded by two lines of German-American Union soldiers, who were unpopular with many native-born Missourians, who resented their anti-slavery and anti-secessionist political views.Many people in St. Louis, having moved to the area from Kentucky, Tennessee, North Carolina, and Virginia, had southern sympathies.