It's no wonder that, at the time, they called it the Great War. World War One was a uniquely horrific war, being the first time that mechanized, industrialized forces were deployed on the battlefield with new-fangled devices like tanks, machine guns, and mustard gas coming into play. As a result of a combination of these new devices with the fact that most armies - or at least, large portions of them - were not yet industrialized in this way, a clash of old and new technology plus old and new ideas about strategy and the ethics of war resulted in literally years of gridlock.
Swaths of French, Belgian, German, Italian, Danish and other fertile farmland were crisscrossed with trenches dug by opposing armies often only a few hundred yards apart, as the two groups ground their own nations and each other into the dust. It lasted four years, and it wiped out an entire generation of young men.
For the first time, battles couldn't and didn't finish when the sun went down, and often there was no clear winner. From Ypres to Verdun to Mons, they would often drag on for days, weeks, or even months, killing tens of thousands of soldiers while budging the front lines precisely not at all.
However, every so often someone would break through - even if their enemy later broke back - and a winner of sorts could be named. Let's see if you recall who claimed that dubious mantle in each of these terrible encounters.