The unit was created on November 26, 1936, at the Madrid front, from the "Ferrer", "Toledo", "Sigüenza", "7th Confederate Militias", "Orobón Fernández" and "Juvenil Libertario" battalions of the Palacios Column. Miguel Palacios Martínez was appointed as commander of the 39th Mixed Brigade, with the anarcho-syndicalist Julián Adrados Almazán as political commissar.