Grant was also concerned about the situation in neighboring Mexico, where 40,000 French soldiers propped up the puppet regime of Austrian Archduke Maximilian. He gave Sheridan permission to gather a large Texas occupation force. Sheridan assembled 50,000 men in three corps, quickly occupied Texas coastal cities, spread inland, and began to patrol the Mexico–United States border. The Army's presence, U.S. political pressure, and the growing resistance of Benito Juárez induced the French to abandon their claims against Mexico. Napoleon III announced a staged withdrawal of French troops to be completed in November 1867. In light of growing opposition at home and concern with the rise of German military prowess, Napoleon III stepped up the French withdrawal, which was completed by March 12, 1867. By June 19 of that year, Mexico's republican army had captured, tried, and executed Maximilian. Sheridan later admitted in his memoirs that he had supplied arms and ammunition to Juárez's forces: "... which we left at convenient places on our side of the river to fall into their hands".