In Western Europe, the war was largely a stalemate as a result of extensive trench warfare that gave the defenders a massive advantage during battles. In Russia, however, the monarchy was overthrown by rebels, who then negotiated peace and surrendered large chunks of land to the Germans, allowing them to concentrate all their troops and resources to the Western Front.
Disease is the answer I believe... If not than it is death by war or massacre
The first mask was made in 7000 BC. It was used primarily for rituals and ceremonies and where typically made of leather or wood. Keep in mind, these where the first masks that our modern generation has been able to find and preserve, masks could have been made earlier than this but detirriorated over time.
However, the first modern surgical masks where made in the early 1960s and replaced a more primitive method of cloth masks.
I hope I have helped! :)
