The idea of opening a second front was essentially the brainchild of Winston Churchill as First Lord of the Admiralty.

He and the First Sea Lord, Jackie Fisher(Father of the Dreadnought and Battle Cruiser) sought to essentially flank the mud and blood to either draw off troops from the main fronts or to strike at the vulnerable heart of the Central Powers.

The various forms of this idea went from seizing the costal islands in the Low Countries, to the isle of Helgoland off the German Coast, to forcing the Skagerrak into the Baltic and supporting a Russian Army as it landed and marched on Berlin.

Eventually this settled on forcing the Bosporus and using the Royal Navy to shell Istanbul into submission and take the Ottomans out of the war. Thus opening a year round water route to get Russian grain out and Western war material in through the Black Sea.

After purely naval attempts failed to force the straits there were calls for the modest commitment of one infantry division that would have gone to Flanders. Just to land and help clear out the Ottoman coastal forts. This blossomed into 10's of thousands of Entente troops, including nearly the whole ANZAC contingent, and was the start of the Gallipoli Campaign. However after the withdrawal forces continued to marshal in Egypt to defend the Canal. And variously successful sideshows in places like Iraq and Salonika drew forces as well.