The establishment of the 45th Division took place at the Aragon Front June 1937 during the planning period of the Huesca Offensive. It was initially foreseen as a provisional unit and even before it became operational General Lukács, the head of the unit grouping, died after being hit by an artillery shell and was replaced by "Emilio Kléber", the first "de facto" commander of the division. 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. Even though it began well at Brunete, the division did not succeed in meeting its assigned targets and ended up suffering numerous casualties.