 The Federal Government reinforced the Arsenal's tiny garrison with several detachments, most notably a force from the 2nd Infantry under Captain Nathaniel Lyon.The other federal arsenal in Missouri, Liberty Arsenal, had been captured on April 20 by secessionist militias and, concerned by widespread reports that Governor Jackson intended to use the Missouri Volunteer Militia to also attack the St. Louis Arsenal and capture its 39,000 small arms, Secretary of War Simon Cameron ordered Lyon (by that time in acting command) to evacuate the majority of the munitions out of the state.21,000 guns were secretly evacuated to Alton, Illinois on the evening of April 29, 1861.