For the bulk of World War I, war on the Western Front was very much a stalemate. This is the famous (or infamous) time of trench warfare.
At the beginning of the war, the Germans mounted an attack that swept into France and was only halted a little bit short of Paris. When they were stopped, they and the Allies dug in in a series of entrenched defensive positions. That was essentially how the war stayed for years.
The trench warfare continued because the defensive technology of the time was much more advanced than offensive technology. There were, at first, very few tanks and little understanding of how to use them. Massed assaults were relatively easily defeated by machine guns and trenches.
Therefore, war on the Western Front was an awful stalemate. Generals still believed in the need for frontal assaults. Therefore, each side launched attacks on the other that were generally fruitless. They introduced poison gas, but all that did was to make life more miserable for both sides. The soldiers had a very hard life, living in dirty trenches that were often wet and cold. They suffered from the elements and from the fighting as well. It was a terrible war.