On March 7, 1861, three days after Abraham Lincoln's inauguration as President of the United States, Isaac left Maryland and traveled to Texas, where he enlisted in the Confederate States Army (serving in the 33rd Cavalry, or Duff's Partisan Rangers, 14th Cavalry Battalion). John Jr. quit his studies at St. Charles College in July 1861 and became a courier for the Confederate Secret Service, moving messages, cash, and contraband back and forth across enemy lines. The Confederate activities in and around Surrattsville drew the attention of the Union government. In late 1861, Lafayette C. Baker, a detective with the Union Intelligence Service, and 300 Union soldiers camped in Surrattsville and investigated the Surratts and others for Confederate activities. He quickly uncovered evidence of a large Confederate courier network operating in the area, but despite some arrests and warnings, the courier network remained intact.