This book is probably long out of print but was recommended by Australian reader Nigel Casson who says the following:

This is a fascinating account by a Frenchman of Spanish descent of his service in the 1st death platoon of the XV th International Brigade. This small unit formed a part of two special companies which served in specialist roles such as reconnaissance, raiding and commando style actions often involving disguising themselves as enemy troops.

According to the book, a platoon was comprised of 3 squads of 5 men led by a sergeant, with 3 platoons to a company. By typical Republican standards they were exceptionally well armed having two light machine guns and a mortar per platoon. Only the most self reliant toughest troops were selected.