Answer:
The sinking of the Lusitania and the Zimmerman telegraph.
Explanation:
The Germans torpedoed and sunk the ship The Lusitania, which killed some of the American passengers on board. This sparked the rallying cry "Remember the Lusitania!" Additionally, the Germans sent what is known as the Zimmerman telegraph to Mexico, trying to forge a Mexican-German alliance and to get Mexico to invade the United States and make them enter the war. This telegram was intercepted however and published.
