The US, the First World War and the Americas (1917–1929) (History HL)

When war broke out in Europe in 1914, President Woodrow Wilson declared the United States neutral. Most Americans agreed — the war seemed a distant European quarrel, and neutrality let US banks and businesses sell goods and loans to both sides.

But neutrality became harder to hold. Britain's navy blockaded Germany, and Germany hit back with unrestricted submarine warfare — sinking any ship near Britain without warning, including neutral and passenger ships. In May 1915 a German U-boat sank the British liner Lusitania, killing 128 Americans. Germany temporarily scaled back submarine attacks to avoid dragging in the US, and Wilson was re-elected in 1916 partly on the slogan "He kept us out of war."

Political, economic, social AND ideological — cover all four: Examiners reward answers that separate the types of reason: political (alliances, German threats to US territory), economic (loans, trade), social (public outrage over lost American lives) and ideological (Wilson's democratic mission). Don't just retell the story — label the reason.

On 2 April 1917, Wilson asked Congress for a declaration of war, and the US formally entered on the side of the Allies. It was less a sudden decision and more the final snap of a rope that had been stretching for three years.

Wilson entered the war believing the US could shape a just and lasting peace, not just win a war. In January 1918 he set out his Fourteen Points — a blueprint including open diplomacy, freedom of the seas, free trade, reduced armaments, national self-determination for European peoples, and — the point closest to his heart — a League of Nations to settle future disputes peacefully.

'Ratification' means Congress saying yes: ratification is a US constitutional requirement — the president can sign a treaty abroad, but two-thirds of the Senate must approve it. This is why Wilson's personal triumph in Paris did not guarantee success at home.

The irony is sharp: the man who designed the League of Nations could not persuade his own Senate to join it. This split — an internationalist president against an isolationist-leaning Congress — shaped US foreign policy through the 1920s.

The war transformed the United States' standing in its own hemisphere. Before 1914, Britain had still been a major financial and naval presence in the Americas. By 1919, the US had become the world's leading creditor nation — Britain and France now owed Washington billions — and US industry, trade and naval power had eclipsed every European rival in the region. The US emerged from the war as the unrivalled hegemon of the Western Hemisphere, its Big Stick and Dollar Diplomacy now backed by unmatched economic muscle.

Choosing your 'one country' for the exam: The syllabus asks for one country of the Americas (besides the US). Canada gives you the richest material — conscription crisis, huge casualties, economic mobilisation — so it is usually the stronger choice for a full essay.

For the impact question, examiners want two countries compared across economic, political, social and foreign-policy angles. The United States and Canada work well together: both industrialised rapidly, both saw women's roles expand, but only Canada faced a conscription-driven unity crisis, while the US faced its own Treaty of Versailles foreign-policy rupture instead.