Hold the fort
This means to take charge and manage until relief or more help arrives. Its origin is from the American Civil War (1861-1865) when General Sherman sent a signal to fellow General Corse who was holding out at Altoona Pass on 5 October 1864. Sherman’s signal actually read, “Hold out: relief is coming.” Philip Bliss (1838-1876) amended it in a Gospel hymn he wrote in 1874 with the refrain, “Hold the fort, for I am coming! Jesus signals still.” The hymn became popular in Britain and since then the expression has passed into the language on both sides of the Atlantic.