Thousand Days' War
On November 3, 1903 Panama separated from Colombia with support from the United States. On November 6 the United States recognized the sovereignty of Panama. On November 11 the United States informed Colombia they would oppose any Colombian troops trying to recover Panama. The Thousand Days' War had left Colombia too weak to prevent the separation. On November 18 the United States signed the Hay–Bunau-Varilla Treaty with Panama for the construction of the Panama Canal.