Hastily formed in the winter in Catalonia shortly before the end of the war and marred by desertions,[3] it was one of the last mixed brigades to be established.

[4] During the period of the instruction of the recruits the commanding officer was Militia Major Lucio Doménech Martínez, following which the 242nd Mixed Brigade was hastily sent to the front and the command of the unit went to Militia Major Julio Marín Serrano.

[4] In the face of the atmosphere of panic and demoralization that preceded the relentless advance of the Francoist armies towards the heart of Catalonia, the constitution of this brigade was fraught with difficulties, mainly because of the high number of fugitives among the young men that had been conscripted.

But practically all other Republican Army units were rushing north towards the French border and the young and inexperienced 242nd Mixed Brigade was not prepared to fight the massive rebel offensive.

[4] On 1 February the brigade was overrun; it quickly lost the nearby towns of Hostalric and Blanes without putting much of a fight and one of its battalions even defected to the enemy as a whole.