When the Civil War began on April 12, 1861, the entire state of Missouri was divided between pro-Confederate and pro-Union forces. Through political connections, and even though a Captain, Lyon was given command of the St. Louis arsenal. He sent almost all the gunpowder and weapons to safety in Illinois. The United States Secretary of War, Simon Cameron, had sent a letter to Lyon, the temporary commander of the arsenal, authorizing him to raise more companies of Union soldiers. It was endorsed by President Abraham Lincoln and Lieutenant general Winfield Scott. Lyon then recruited thousands of untrained volunteers from among the German community in St. Louis. Most German immigrants were against slavery which made them unpopular among many of the city's pro-Confederate citizens.