On April 6, 1917, the United States entered World War I after the U.S. House of Representatives followed the lead of the U.S. Senate in approving a declaration of war against Germany. The decision was a divisive one at the time, and it remains controversial a century later. On the centennial of America’s entry into the Great War, explore the historical debate about whether that decision was a correct one or not.

The Case for U.S. Entry into World War I

Woodrow Wilson asking Congress to declare war on Germany.
Woodrow Wilson asking Congress to declare war on Germany. (Credit: Photo12/UIG via Getty Images)

On January 22, 1917, President Woodrow Wilson told a joint session of Congress that the United States must remain neutral in World War I to ensure “peace without victory.” Eleven weeks later, he returned to Congress to request a declaration of war against Germany.

The rapid turn of events was brought on by a series of German actions that some historians believe left Wilson with little choice but to finally enter the war in Europe. Scores of American civilians had already been killed by German U-boats since the beginning of the war, including 128 in the 1915 sinking of RMS Lusitania. The following year German saboteurs detonated the Black Tom munitions depot in Jersey City, New Jersey, killing seven people and strafing the Statue of Liberty with shrapnel.

For two years, Wilson repeatedly warned the Germans against a policy of unrestricted submarine warfare, which he considered a violation of international law and a pretext to a break in diplomatic relations. “Germany made the decision for reasons dealing with internal politics in January 1917 to go to unrestricted submarine warfare in defiance of the threats,” says historian Ross Kennedy, a professor at Illinois State University and author of “The Will to Believe: Woodrow Wilson, World War I, and America’s Strategy for Peace and Security.” “Wilson had no choice but to break relations or he would have lost diplomatic credibility.”

American Heroes of WWI

Even after announcing the diplomatic break on February 3, 1917, Wilson still signaled that the United States would stay out of the war as long as the Germans did not target American vessels. Then came the publication of the Zimmerman Telegram in which Germany proposed secret military and financial support for a Mexican attack on the United States, should it enter the war, and in exchange Mexico would be free to annex “lost territory in Texas, New Mexico and Arizona.” Kennedy says the Zimmerman Telegram caused a stir but the major precipitating event for the declaration of war occurred in mid-March when “the Germans sank three American merchant ships in rapid succession—American ships under American flags with American crews—a direct attack on American sovereignty.”

“Given the U.S. policy and German actions, it’s hard to see any president not doing what Wilson did at that point,” Kennedy says. “He has to follow through and go for the war declaration given the earlier policy. Wilson’s whole credibility and the credibility of the country is on the line.” Kennedy points out that by drawing red lines earlier in the war, Wilson had put himself in a box where war was nearly unavoidable by April 1917.

Kennedy says that most historians agree that American entry into World War I tipped the scales against Germany and that without the participation of the United States the Allies would have lost, “defined as having to make a compromise peace with the Germans largely on German terms.” Things weren’t going well for the Allies by the spring of 1917. They had suffered a big setback in Italy, the French army faced a serious mutiny problem and Russia was teetering after the overthrow of the tsar, which would lead to the eventual loss of the Eastern Front.

A military parade with crowds of excited spectators along 5th Avenue, in celebration of Armistice day and peace in Europe following World War One, New York, 1918. (Photo by Paul Thompson/FPG/Getty Images)
A military parade with crowds of excited spectators along 5th Avenue, in celebration of Armistice day and peace in Europe following World War One, New York, 1918. (Photo by Paul Thompson/FPG/Getty Images)

The Allies were not only exhausted emotionally and militarily—but financially as well. “They were in serious financial trouble in early 1917,” Kennedy says. “They depended heavily on American banks to finance their purchases of war supplies, and their ability to get those loans was becoming harder and harder. One of the immediate benefits after the United States enters is that Wilson gets Congress to pass legislation to allow the U.S. government to loan money to the Allies. Those government-to-government loans give them the money to fund their purchases of crucial supplies.”

“Even with the U.S. entry,” Kennedy says, “the British in late 1917 were seriously contemplating peace feelers from the Germans under which the Germans would have kept all their gains on the Eastern Front and pulled back in the west. If the Americans hadn’t entered the war, the British would have done that deal.”

There are some historians who make the case that Imperial Germany would eventually have become an American menace had it emerged victorious as a result of the United States remaining on the sidelines, though certainly not to the extent of the Third Reich. So what terms would have the Germans dictated as victors? They may not have been as punitive as those eventually enacted by the Allies, but the Treaty of Brest-Litovsk that Germany negotiated with the new Bolshevik government of Russia in 1918 took a hard line.

Russia was forced to recognize the independence of Ukraine, Georgia and Finland and ceded Poland and the Baltic states of Lithuania, Latvia and Estonia to Germany and Austria-Hungary. In all, Russia lost 55 million people; gave up a majority of its coal, oil, and iron stores; and had its industry gutted under the agreement, which was annulled by the Armistice of November 11, 1918.

The Case against U.S. Entry into World War I

Women carrying peace banner during an international protest against war. (Credit: Bettmann/Getty Images)
Women carrying peace banner during an international protest against war. (Credit: Bettmann/Getty Images)

“I think the United States should only go to war when it’s in our national interest, when we are really threatened, and when morally it could be defined as a ‘just war,’ and I don’t think any of those occurred in World War I,” says historian Michael Kazin, a professor at Georgetown University and author of “War Against War: The American Fight for Peace 1914-1918.”

Plenty of Americans shared the same sentiment in April 1917. The country was hardly united in the decision to declare war on Imperial Germany, as the 56 votes against the measure in Congress attested. Less than six weeks before the war declaration, anti-war senators had even led a successful filibuster to block a proposal to arm American merchant ships with U.S. naval personnel and equipment. A peace coalition of an unprecedented size and diversity attempted to keep the United States from entering the battlefields. The strange bedfellows included progressive Republicans and Southern Democrats as well as socialist labor leaders such as Eugene V. Debs and business magnates such as Henry Ford. “They disagreed about many things,” Kazin says, “but they all agreed that militarizing American society would turn the United States into a very different country where the military would be calling the shots more.”

Kazin says there was no immediate threat to the security of the United States from Imperial Germany in 1917 because it was incapable of launching a trans-Atlantic attack. “Unlike in World War II when Hitler had long-range planes and a larger navy, there was no threat of Germany invading the United States,” he says.

French soldiers of the 370th Infantry Regiment during the battle of the Aisne, 1917.
French soldiers of the 370th Infantry Regiment during the battle of the Aisne, 1917. (Credit: Galerie Bilderwelt/Getty Images)

Detractors of the American entry into World War I argue that by tipping the scales to the Allies, the United States didn’t hasten the end of the war but actually prolonged it by removing the incentive for the British and French to make a negotiated peace with Germany as the battle stalemated in 1917. The ensuing punitive peace also laid the groundwork for an even deadlier world war a generation later and the rise of the Nazis. “It was unclear that by supporting the Allies that the United States would be able to put together the ‘peace without victory’ that Wilson wanted,” Kazin says. “As the peace coalition predicted, after all those years of losing millions of people, the victorious powers were not going to be in a mood to be kind to those who lost.”

The decision to enter World War I led not only to the deaths of more than 116,000 Americans abroad but to the trampling of civil liberties at home. “If there should be disloyalty, it will be dealt with a firm hand of stern repression,” Wilson warned in his address to the joint session of Congress. It was. The Espionage Act of 1917 and Sedition Act of 1918 curtailed speech, vigilantes with the American Protective League physically assaulted anti-war activists, mail and newspapers were censored and radicals such as Emma Goldman were deported.

(GERMANY OUT) First World War trenches at Vimy Ridge National Historic Site of Canada, France.   (Photo by Forster/ullstein bild via Getty Images)
(GERMANY OUT) First World War trenches at Vimy Ridge National Historic Site of Canada, France. (Photo by Forster/ullstein bild via Getty Images)

“In terms of free speech, it was the most repressive period in American history,” Kazin says.“It became potentially illegal to speak out against the war, disparage the president or try to organize people to restrict the draft. There was an atmosphere of fear. The socialist press was basically put out of business when the postmaster general denied second-class mailing privileges. Wilson made it very clear that he wasn’t going to allow any kind of dissent that went against the mission. Leaders of the left were put in jail. It had a chilling effect on other dissenters.”

Kazin argues that it was hardly a foregone conclusion that the Allies would have lost World War I had the United States not joined the fight. “The Germans were not doing well either in 1917. The most popular party in the Reichstag was already split, and there was a lot of disaffection among ordinary Germans. One reason the German military wanted to win quickly with unrestricted submarine warfare was they were worried about the country coming apart.”

Even had Germany won World War I if the United States stayed on the sidelines, Kazin says it still wouldn’t have posed an existential threat. “The political complexion would have been quite different than under the Third Reich. Germany might have evolved into more of the social democratic society it is today. Certainly Hitler’s party was able to exploit Germany’s loss in the war, which was a major reason why Germany rearmed and World War II happened.”