The allies invaded Paraguay in April 1866, but after initial success, their advance was blocked by fortifications at Humaitá by land and along the Paraguay River. The Progressive cabinet decided to create a unified command over Brazilian forces operating in Paraguay, and it turned to the 63-year-old Caxias (made permanent army marshal on 13 January) as the new leader on 10 October 1866. He told his wife that the reason he had accepted the post was because the war "was an evil that has reached more or less all, from the Emperor to the most unfortunate slave."