In trench warfare five things are important: firewood, food, tobacco, candles, and the enemy. In winter on the Zaragoza front they were important in that order, with the enemy a bad last. Except at night, when a surprise-attack was always conceivable, nobody bothered about the enemy. They were simply remote black insects whom one occasionally saw hopping to and fro. The real preoccupation of both armies was trying to keep warm.
-George Orwell, Homage to Catalonia
Ed. Note: The war was the Spanish Civil War. The time was 1936ish. Where Orwell was reporting from, neither side had artillery.