7.5 World War I: Military and Diplomacy

7 min readdecember 27, 2022

Robby May

Robby May

Caleb Lagerwey

Caleb Lagerwey



AP US History 🇺🇸

454 resources
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Causes of WWI

World War One (WWI) broke out in Europe in 1914 and quickly involved much of the world thanks to European colonies and alliances that reached all of the globe. While it might not be completely necessary to know all about the war and its origins, a quick acronym can help you remember the causes of the war:
Militarism - countries building up militaries in an arms race
Alliances - each country had friends, so any conflict could easily spread
Nationalism - each country thought they were the best and others were evil
Imperialism - European countries competed for territory and spread out
Assassination - a Serbian nationalist killed Austria-Hungary’s archduke Franz Ferdinand, which sparked the war because of underlying tensions (see above)
The sides eventually looked something like this (major players worth knowing):
🔥 Trivia: AP US History - Progressive Era and WWI Trivia
Central Powers
Ottoman Empire
Great Britain
Russia (until 1917)
USA (after 1917) (spoiler!)

Initial Neutrality to Entrance

In good ol’ (George) Washingtonian tradition, the US tried to stay neutral and out of foreign alliances. The president at the time, Woodrow Wilson, wanted to keep the US out of WWI for a variety of reasons, not least because the US was a nation of immigrants (Germans vs. British, especially) and because he wanted the US to play an impartial role in making a peace deal. 
This neutrality started to fail because of a few facts/events.

Loaning of Money

The US was loaning vastly more money to the Allies (about $2.5 billion eventually) than to the Central Powers ($56 million). This diplomatic action placed American interests primarily in the Allies and created a political rift between the US and Germany in particular.

German U-Boats and Sinking of the Lusitania 

Second, although the British were stopping US ships trying to trade with the Central Powers using their superior blue-water navy, they usually confiscated and bought the trade goods. The Germans, by contrast, could not compete with the British Navy and relied on U-Boats, or submarines. This meant they attacked Great-Britain-bound goods from underwater and did not confiscate or compensate. In fact, they often destroyed lives too as the boats they attacked sank with crew and cargo. 
The most famous incident was the sinking of the HMS Lusitania in 1915, which killed 123 Americans. (The boat was also carrying weapons for the British in violation of US neutrality, but the US initially denied it). The US did NOT join the war at this point, partly because the Germans apologized and pledged not to sink US ships again, but…

Zimmerman Telegram

Third, the Zimmerman Telegram and resumption of unrestricted submarine warfare in 1917 tipped the scales and the US joined the war. The Zimmerman telegram was a message from Germany to Mexico—decoded and shared by the British—that urged Mexico to invade the US to keep the US occupied in exchange for German support for Mexico taking back parts of the Mexican Cession (1848). This outraged the US. In that telegram, the Germans also announced they would be going back on their pledge not to sink US ships. They gambled that they could starve Great Britain into peace talks before the ticked-off US had time to mobilize and react. They were almost right. 
Finally, Woodrow Wilson, who had initially won reelection in 1916 with the slogan “He kept us out of war!”, framed the war in humanitarian terms and with democratic values.
He said we needed to help Europe resist German despotism/tyranny and to “make the world safe for democracy” by allowing each country to rule itself without outside interference. He meant without German militarism taking over, but failed to see the hypocrisy when it came to imperialism/colonialism 


Many recognized that the US military was hopelessly unprepared for a major war. They pushed for “preparedness” (greater defense expenditures). 
Wilson urged Congress to approve an ambitious expansion of the armed forces. After a nationwide speaking tour on behalf of preparedness, Wilson finally convinced Congress to pass the National Defense Act in June 1916, which increased the regular army to a force of nearly 175,000. Congress then approved the construction of more than 50 warships in just one year. 
🎥 Watch: AP US History - Progressive Era and WWI

US in Combat

Although not a huge deal in APUSH, it helps to know a bit about what warfare was like during WWI. WWI is considered by some the first truly industrialized war, with all kinds of nasty inventions being used to kill humans for the first time on a massive scale: trenches, fully-automatic machine guns, air planes, poison gas, and tanks made the war truly horrific, especially when paired with the initial, outdated tactics used by both sides that resulted in terribly costly charges against entrenched enemies. 
The US eventually registered 9.5 million men for the draft after the passage of the Selective Service Act in 1917. Most of the American Expeditionary Force, commanded by General John K. (Blackjack) Pershing, got to France and saw combat by early 1918. The AEF saw significant victories in Chatteau-Thierry and Belleau Wood on the Western Front.
For the first time US troops were shipped oversea in late 1917, millions of European soldiers on both sides had already died in trench warfare made more murderous in the industrial age by heavy artillery, machine guns, poison gas, tanks, and airplanes.
The exhausted Germans had tried to break the exhausted British and French before the US could arrive—they got to within 50 miles of Paris—but they failed to win before the sheer number of American soldiers tipped the scales in favor of the Allies.
Battles like Meuse-Argonne between the US and Germany helped to force Germany into an armistice, or truce, while they ironed out the details of a peace treaty, eventually called the Treaty of Versailles.
After only a few months of fighting, US combat deaths totaled nearly 49,000. Many more thousands died of disease, including a flu epidemic in the training camps, bringing the total US fatalities in WWI to 112,432.

A map of some actions taken by the AEF

Fourteen Points

Even though Woodrow Wilson and the US were a large part of the war and of the peace settlement— Wilson traveled over to France for the peace conference. This was the first time in American history that a president had personally traveled outside of the US for peace negotiations. He upset the Senate when his delegation to the conference did not include a Senator and only one Republican, which would end up being a politically fatal mistake for him.
In his hands, he would carry his Fourteen Points, which he envisioned as a part of the treaty. Some of the points included:
  • Recognition of freedom of the seas
  • An end to the practice of making secret treaties
  • Self-determination for the various nationalities
  • Removal of trade barriers
  • A general association of nations (the League of Nations) for the purpose of affording mutual guarantees of political independence and territorial integrity to great and small states alike. This was the point that Wilson valued the most and would soon be named the League of Nations. It formed the political basis for the eventual United Nations in the modern day

Treaty of Versailles

Other heads of state at Versailles made it clear that their nations wanted both revenge against Germany and compensation in the form of indemnities and territory
France and Great Britain agreed to form the League of Nations, but insisted on blaming Germany for the war and making Germany pay for the cost of the war. This would eventually backfire. The Treaty of Versailles included the following (use the handy acronym BRAT to remember it): 
  • B - Germany had to accept the sole blame for the war.
  • R - Germany was forced to pay billions of dollars in reparations (financial damages) to the Allies. This ended up breaking the back of the German economy. 
  • A - Germany had to give up most of its army
  • T - Germany lost all of its colonial territory as well as some of its territory in Europe. In addition, the League of Nations was established.

Senate Debate on Treaty

The US Senate, constitutionally in charge of approving treaties, rejected both the Treaty of Versailles and the League of Nations. Senators, especially traditionally isolationists ones in the Midwest, objected to Article X of the treaty, which would have denied Congress its right to declare war by mandating military involvement in any war against aggressor nations. 
Wilson refused to accept the denial of the Senate, so he took his appeal directly to the American people. He traveled all across the US giving speeches to Americans to get them to support the treaty. 
When Wilson returned to the White House he felt ill. That night Mrs. Wilson found him unconscious on the floor of the White House. He had a massive stroke that paralyzed his left side. After the stroke, he could not work more than an hour or two at a time. No one was allowed to see him except family, his secretary and his physician. For over 7 months he did not meet with the cabinet. His wife, Edith Wilson ran the government. 
Democrats told Wilson they could not pass the treaty without reservations. Wilson refused to compromise, so the treaty failed in the Senate. 
The US then entered a period of isolationism or unilateralism in the 1920s...
🎥 Watch: AP US History - World War I
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