It would become especially renowned for providing desperately needed support in the darkest hours of the Republican defense of Madrid on 8 November 1936, when, with great losses, it helped repulse a major assault by veteran Nationalist troops, buying time for more Republican troops to be brought into the city.

[1] It was originally mustered from international volunteers at Albacete, Spain, in mid-October 1936 as the IX Brigada Movíl, with four battalions: It was redesignated the 'XI "Hans Beimler" International Brigade' on 22 October 1936, with General "Kléber" (Manfred Stern) commanding.

[11] After the death of Hans Beimler the energetic Giuseppe Di Vittorio became the political commissar.

On 18 July 1956, the German Democratic Republic issued the Hans Beimler Medal to veterans of the XI International Brigade, and other volunteer units in Spain.

[12] The medal is silver with a relief portrait of Hans Beimler on one side, and the three-pointed star of the International Brigades on the reverse, with the inscription "KAMPFER FVR SPANIENS FREIHEIT 1936-1939", Fighters for Spanish Liberty (1936–1939).