If you’re looking for chronology and clarity from one of the most infamous and drawn out battles in British history then this excellent section from the Commonwealth War Graves Commission’s Histories series is a good place to begin.

The Battle of the Somme is revealed stage by stage with clear descriptions of the events and places that have now entered the soldier’s mythology as scenes of unbelievable carnage and slaughter.

You can also refer to handy elements such as a clear campaign map, sections explaining army structure, terminology and an image library.

An essential guide for students or a handy primer for battlefield visitors to the region.  

http://www.cwgc.org/somme