When war broke out in August 1914, America had been quick to declare its neutrality, stating that it had no wish to become embroiled in what it regarded as a European squabble.
Yet over the following three years, a series of provocations slowly but surely nudged the America people towards the Allied camp.
First there was the news of German atrocities in Belgium in 1914, then the German sinking of the liner RMS Lusitania (killing many Americans) in 1915. Yet perhaps most significant of all was the German decision to resume all-out submarine warfare on commercial shipping heading to Britain, which would inevitably include American vessels.
This outraged American public opinion, and when the US government got wind of German plans to strike up an alliance with America’s long-term rival Mexico, the die was cast. American president Woodrow Wilson felt he had no choice but to declare war.