After the crashing failure of the new unit at the combats of the Huesca Offensive in June, the 45th Division was brought to the Madrid Front in order to take part in the Battle of Brunete under Kléber's leadership.

Owing to the poor performance of the unit under his command, Kléber was replaced by Hans Kahle and the human losses were covered by new reinforcements.

[1] During the offensive the division held its ground against the deadly attacks of the Francoists, ending up with a very high number of casualties, especially the XIV International Brigade —part of the division— which suffered huge losses during the failed attempt to cross the Ebro River near Amposta.

It is known that the 45th Division took part in the first hopeless Republican efforts of trying to contain the rebel onrush of the Catalonia Campaign, but it soon had to withdraw northwards to the French border.

After crossing the frontier line in early February 1939 the fleeing Republican troops were disarmed and interned in concentration camps by the French authorities and the division was terminated.