Animals

They used animals to attach bombs and send it to the other side, like dogs and cats. They did not give food to the animals so they were very hungry and would run to the other side. They had a button so they could press it and the animals would explode. They used pigeons to send messages. In the trenches there were many rats. When the soldiers were very hungry they would eat the rats.

Picture from: https://denstorekrig1914-1918.dk/29-oktober-1916-desertoeren-jakob-moos-forfulgt-af-en-rasende-vagthund/