Initially, the United States maintained a neutral stance as World War I erupted in Europe. However, by 1917, this policy dramatically shifted, culminating in America’s entry into the global conflict. President Woodrow Wilson, who initially sought to keep the nation out of war, ultimately requested a declaration of war against Germany on April 2, 1917, addressing a joint session of Congress. This pivotal moment begs the crucial question: why did America join World War I? The answer lies in a complex web of factors, primarily driven by Germany’s aggressive actions and their implications for American interests and global security.
Germany’s decision to reinstate unrestricted submarine warfare in the early months of 1917 proved to be a critical turning point. This policy directly violated Germany’s earlier commitment, known as the “Sussex pledge,” made to the United States in 1916. The pledge had been a response to American outrage following the sinking of the French passenger vessel Sussex. Germany had agreed to refrain from attacking passenger ships and to allow crews of merchant vessels to evacuate before any attacks.
By January 1917, facing a stalemate on the Western Front and dire economic conditions due to the Allied blockade, German military leaders believed that a swift victory could be achieved by crippling Great Britain’s supply lines through unrestricted submarine attacks. They calculated that even if this policy provoked the United States, German U-boats could force Britain to surrender before American troops could effectively mobilize and intervene in Europe. German policymakers reasoned that the U.S. had already compromised its neutrality by supplying the Allied nations with munitions and financial aid, thus justifying the violation of the Sussex pledge. They also argued that America had tacitly accepted the Allied blockade against Germany, further eroding its neutral status.
World War I Trenches in France: A stark depiction of the brutal trench warfare that characterized much of World War I, highlighting the conditions that American soldiers would soon face following the US entry into the conflict.
Despite warnings from German Chancellor Theobald von Bethmann-Hollweg, who foresaw that renewed submarine warfare would inevitably draw the United States into the war and ultimately lead to Germany’s defeat, the German government proceeded with this perilous strategy. On January 31, 1917, Germany officially informed the United States of its intention to resume unrestricted submarine warfare.
President Wilson was deeply troubled by this announcement. On February 3, he addressed Congress to declare the severance of diplomatic ties with Germany. However, he hesitated to immediately request a war declaration, uncertain whether American public opinion was prepared for war without undeniable proof of German aggression against U.S. ships. Wilson still held out hope for negotiation if Germany ceased targeting American shipping. Despite Wilson’s reservations, German submarines relentlessly began attacking U.S. vessels throughout February and March 1917, resulting in the tragic deaths of numerous American sailors and civilians.
In response to these attacks, and recognizing the growing threat, Wilson sought congressional authorization on February 26 to arm American merchant ships with U.S. Navy personnel and weaponry. While this measure likely had sufficient support to pass, anti-war senators successfully employed a filibuster, stalling the legislation. Undeterred, President Wilson resorted to an executive order, invoking an old anti-piracy law to arm merchant ships, demonstrating his resolve to protect American interests on the seas.
Concurrently, the revelation of the Zimmermann Telegram added another layer of complexity and urgency to the situation. On January 19, 1917, British naval intelligence intercepted and deciphered a secret communication from German Foreign Minister Arthur Zimmermann to the German Ambassador in Mexico. This infamous “Zimmermann Telegram” proposed a military alliance between Germany and Mexico in the event of the United States entering the war. Germany pledged to assist Mexico in reclaiming territories lost to the U.S. during the Mexican-American War, including Texas, New Mexico, and Arizona.
German Chancellor Theobald von Bethmann-Hollweg: A portrait of the German Chancellor who opposed the resumption of unrestricted submarine warfare, understanding it would provoke the United States and lead to German defeat in World War I.
Initially, British intelligence withheld the Zimmermann Telegram from the U.S. to protect their code-breaking operations. However, with Germany’s resumption of unrestricted submarine warfare and the escalating crisis, the British recognized the telegram’s potential to galvanize American public and political support for war. The British government finally presented the intercepted telegram to President Wilson on February 24. The American press widely publicized the sensational news the following week, igniting public outrage and solidifying anti-German sentiment across the United States.
Despite the inflammatory nature of the Zimmermann Telegram, President Wilson still proceeded cautiously towards war. It wasn’t until March 20 that he convened his Cabinet to deliberate on the matter—nearly a month after receiving the telegram. Historians continue to debate the precise factors that ultimately compelled Wilson to choose war in 1917, especially considering his previous efforts to maintain neutrality following earlier crises like the sinking of the Lusitania and Arabic in 1915.
However, by 1917, the confluence of Germany’s relentless submarine attacks on American ships, resulting in civilian casualties, and the provocative Zimmermann Telegram, suggesting a potential German-backed attack on American soil, significantly shifted American public opinion. The idea of armed neutrality became increasingly untenable. Furthermore, international law at the time suggested that arming U.S. merchant ships with naval personnel to defend against submarines could already be construed as an act of war against Germany. Ultimately, Germany’s actions demonstrated a clear unwillingness to pursue a peaceful resolution to the conflict.
The “Zimmermann Telegram”: A photograph of the decoded Zimmermann Telegram, a secret communication from Germany to Mexico proposing a military alliance against the United States, which significantly swayed American public opinion towards entering World War I.
These converging factors—Germany’s unrestricted submarine warfare, the Zimmermann Telegram, and the resulting shift in American public and political opinion—collectively propelled President Wilson to request a declaration of war against Germany. Congress, recognizing the gravity of the situation and the imperative to defend American interests and international law, granted Wilson’s request, formally declaring war on Germany and marking the United States’ entry into World War I.
