It was initially formed entirely of volunteers, "chiefly composed of Polish miners recently living and working in France and Belgium".

[10] This battalion was originally part of XI Brigada Movil ("11th Mobile Brigade") which was formed 14–17 October 1936.

The first Brigade to arrive was the XI with 1,700 men, mainly Germans, French, Belgians and Poles, followed by the XII four days later with another 1,550.

The CNT press in the capital reported their arrival in the early hours of the morning 'in silent and damp streets: Marching firmly, their footsteps echoing on the cobblestones... singing revolutionary songs in French, German, Italian...

***CITATION***The Dabrowski Battalion was in the thick of the action - at the University City and Casa de Campo - losing two thirds of its men.

The Dąbrowski Battalion, as part of the XII brigade, was sent to Jarama, a few kilometres from Madrid, to block a Nationalist attack.

As its numbers were reduced by casualties, it absorbed various other understrength international battalions, supplemented by Spanish conscript companies, but it never again reached full strength.