The Sussex Pledge was a promise given by the German Government to the United States of America on May 4, 1916, in response to US demands relating to the conduct of the First World War. Specifically, Germany promised to alter its naval and submarine policy of unrestricted submarine warfare to stop the indiscriminate sinking of non-military ships. Instead, merchant ships would be searched and sunk only if they contained contraband, and then only after safe passage had been provided for the crew and passengers.

The Sussex Pledge Issued

On March 24, 1916, a German submarine in the English Channel attacked what it thought was a minelaying ship. It was actually a French passenger steamer called 'The Sussex' and, although it didn't sink and limped into port, fifty people were killed. Several Americans were injured and, on April 19th, the US President (Woodrow Wilson) addressed Congress on the issue. He gave an ultimatum: Germany should end attacks on passenger vessels, or face America 'breaking off' diplomatic relations.

Germany's Reaction

It's a huge understatement to say Germany didn't want America to enter the war on the side of her enemies, and the 'breaking off' of diplomatic relations was a step in this direction. Germany thus responded on May 4th with a pledge, named after the steamer Sussex, promising a change in policy. Germany would no longer sink anything it wanted to at sea, and neutral ships would be protected.

Breaking the Pledge and Leading the US into War

Germany made many mistakes during World War I, as did all the nations involved, but their greatest after the decisions of 1914 came when they broke the Sussex Pledge. As the war raged on in 1916, the German High Command became convinced that, not only could they break Britain using a full policy of unrestricted submarine warfare, they could do it before America was in a position to fully join the war. It was a gamble, one based on figures: sink x amount of shipping, cripple the UK in y amount of time, establish peace before the US could arrive in z. Consequently, on February 1, 1917, Germany broke the Sussex Pledge and returned to sinking all 'enemy' craft. Predictably, there was outrage from the neutral nations, who wanted their ships left alone, and something of a relief from Germany's enemies who wanted the US on their side. American shipping began to sink, and these actions contributed heavily to America's declaration of war on Germany, issued April 6, 1917. But Germany had expected this, after all. What they had got wrong was that with the US Navy and the use of the convoy system to protect ships, the German unrestricted campaign could not cripple Britain, and US forces began to be moved freely across the seas. Germany realized they were beaten, made one last throw of the dice in early 1918, failed there, and ultimately asked for a ceasefire.

President Wilson Comments on the Sussex Incident

"...I have deemed it my duty, therefore, to say to the Imperial German Government, that if it is still its purpose to prosecute relentless and indiscriminate warfare against vessels of commerce by the use of submarines, notwithstanding the now demonstrated impossibility of conducting that warfare in accordance with what the Government of the United States must consider the sacred and indisputable rules of international law and the universally recognized dictates of humanity, the Government of the United States is at last forced to the conclusion that there is but one course it can pursue; and that unless the Imperial German Government should now immediately declare and effect an abandonment of its present methods of warfare against passenger and freight carrying vessels this Government can have no choice but to sever diplomatic relations with the Government of the German Empire altogether.

This decision I have arrived at with the keenest regret; the possibility of the action contemplated I am sure all thoughtful Americans will look forward to with unaffected reluctance. But we cannot forget that we are in some sort and by the force of circumstances the responsible spokesmen of the rights of humanity, and that we cannot remain silent while those rights seem in process of being swept utterly away in the maelstrom of this terrible war. We owe it to a due regard to our own rights as a nation, to our sense of duty as a representative of the rights of neutrals the world over, and to a just conception of the rights of mankind to take this stand now with the utmost solemnity and firmness..."