Hancock went to Gettysburg anyway. "I got into Gettysburg the night of July sixth – where the need was so great that there was no further cavil about age,” she wrote in her journal. In a letter to her sister dated July 8, 1863, Hancock wrote, "We have been two days on the field; go about eight and come in about six—go in ambulances of army buggies...I feel assured I shall never feel horrifed at anything that may happen to me here-after." Hancock responded to an immense need: the Union lacked supplies as well as staff. She had no formal training as a nurse; but after three weeks, she was tending to eight tenths of wounded. In October she tended to the large numbers of hungry and injured escaped slaves who were arriving in Washington, D.C.