In June 1917 at the start of the Battle of Messines, the forces of the British Commonwealth faced off against the German Army. 19 huge land mines were detonated, tearing apart the German lines, and with them, the fabric between the natural and Supernatural.
Supernatural creatures issued forth and the western front crumbled as both sides struggled to contend with the new enemy. Russia soon fell to a resurrected Rasputin and his Demon spawned allies, the Middle East struggled against the cults of Moloch which created shockwaves through to the Mediterranean.
The emergence of a new enemy and cult at the Bermuda triangle saw the America struggle. The South Pacific, Australia and New Zealand would disappear under a fog created from the rising of a mammoth volcanic continent North east of New Zealand.
Yet despite the threats, mankind continued to fight each other. Old enemies and grudges reappeared, the Prussians invaded New Guinea, and China invaded Manchuria and Japan.
Dark World War is a simple game system, it can be played at a company level or larger if players wish. Traditional forces battle against creatures from Mythology and Hell.
The rules are "pay what you want" but can be downloaded for free here.