Men used to write to their families while sitting in the trenches and women wrote to their husbands and sons from home. The British Post Office was well known for making sure all letters were delivered even to the trenches.
But something was still missing. So women began buying postcards with sentimental poems on them. The most famous was called "The Vacant Chair"
Most of these postcards used poems written before the war and added to cards that were specially painted.