The first poem I learned by heart was Wilfred Owen’s “Dulce et Decorum Est” (here)
Knock-kneed, coughing like hags, we cursed through sludge,Till on the haunting flares we turned our backs,And towards our distant rest began to trudge.Men marched asleep. Many had lost their boots,But limped on, blood-shod. All went lame; all blind;Drunk with fatigue; deaf even to the hootsOf gas-shells dropping softly behind.
If any question why we died,Tell them, because our fathers lied.