Here is the lore of the Death Korps. Hope ya like it :)

  In a galaxy in the year 40,000, humans are dying out. Many are lost against aliens and the chaos gods' followers. Humans are on the brink of extinction, no matter how hard they try to hold out. The Death Korps, one of the human armies, fight to hold the line. They wear gas masks into battle, obscuring their faces. The send in millions of soldiers every day to defend humankind. Their bayonets on their rifles piece the enemy's skin, and their lasguns roar their fury at the enemy.

  Note that the lore is from the board game/video game Warhammer 40k.