and at first, she was allowed to practice only as a nurse. During this period, she served at the First Battle of Bull Run (Manassas), July 21, 1861, and at the Patent Office Hospital in Washington, D.C. She worked as an unpaid field surgeon near the Union front lines, including at the Battle of Fredericksburg and in Chattanooga after the Battle of Chickamauga. As a suffragist, she was happy to see women serving as soldiers, and alerted the press to the case of Frances Hook, in Ward 2 of the Chattanooga hospital, a woman who served in the Union forces disguised as a man. Walker was the first female surgeon of the Union army. She wore men's clothing during her work, claiming it to be easier for high demands of her work. In September 1862, Walker wrote to the War Department requesting employment as a spy, but her proposal was declined. In September 1863, she was employed as a "Contract Acting Assistant Surgeon (civilian)" by the Army of the Cumberland, becoming the first female surgeon employed by the U.S. Army Surgeon. Walker was later appointed assistant surgeon of the 52nd Ohio Infantry. During her service, she frequently crossed battle lines and treated civilians. On April 10, 1864, she was captured by Confederate troops, and arrested as a spy, just after she finished helping a Confederate doctor perform an amputation. She was sent to Castle Thunder in Richmond, Virginia, and remained there until August 12, 1864, when she was released as part of a prisoner exchange. While she was imprisoned, she refused to wear the clothes provided her, said to be more "becoming of her sex". Walker was exchanged for a Confederate surgeon from Tennessee on August 12, 1864. She went on to serve as supervisor of a female prison in Louisville, Kentucky, and as the head of an orphanage in Tennessee. Later career After the war, Walker was awarded a disability pension for partial muscular atrophy suffered while she was imprisoned by the enemy. She was given $8.50 a month, beginning June 13, 1865, but in 1899 that amount was raised to $20 per month. She became a writer and lecturer, supporting such issues as health care, temperance, women's rights, and dress reform for women. She was frequently arrested for wearing men's clothing, and insisted on her right to wear clothing that she thought appropriate. She wrote two books that