Was the British blockade more moral than the U-boat war?

The short answer

• The fleet and its diplomatic purpose. Admiral Tirpitz intended the “risk fleet” to make a war against Germany so dangerous that Britain would prefer neutrality and concessions, including colonies. Naval rivalry instead deepened British suspicion and helped bring Britain closer to France and Russia. Germany's fleet could challenge Britain but could not reliably defeat it, and its leaders hesitated to risk its loss. Long periods in port later formed part of the background to the sailors' mutiny in 1918 (Chapter 13). The fleet had influenced diplomacy even when it remained in harbor.
• Two methods of economic pressure. Britain treated food as “contraband” and diverted neutral ships into its ports. The United States protested, although Britain settled claims for losses. German submarines faced danger in stopping vessels for inspection; unrestricted attacks instead sank ships without warning. Both campaigns sought to deny supplies to an enemy, but the deaths of 1,198 people aboard the Lusitania were immediate and conspicuous. Hunger was harder to see and its death toll harder to establish. This helps explain the difference in public reaction; it does not settle the legal or moral questions.
• The five-month calculation. Holtzendorff's staff study estimated shipping sunk, neutral tonnage frightened away and the duration of British food reserves. Its conclusion was victory in five months, “before a single American soldier sets foot on the continent.” The decision went against the Chancellor's judgment. Yet the calculation depended on how merchants and governments would respond as well as on sinkings. Convoy, rationing and American shipbuilding could alter that response. Precise inputs could not guarantee the prediction.
• The argument over convoy. The Admiralty's objections to convoy included practical questions: could merchant captains keep station, and would gathering ships congest ports? Escorts were wanted elsewhere, while a navy accustomed to seeking the enemy hesitated to guard freighters. Junior officers and a civilian ministry challenged the figures used against convoy, arguing that the reported “weekly 5,000 sailings” was inflated about twentyfold. Prime-ministerial pressure helped secure adoption. The decision put existing ships and escorts to work in a different arrangement.

What it changed

The United States enters. The United States entered the war on 6 April 1917 after unrestricted submarine warfare and the Zimmermann telegram helped end its neutrality. The telegram, intercepted by British codebreakers, proposed a German alliance with Mexico against the United States. American loans, food, steel and shipping strengthened an Entente whose dollars and credit were under pressure. Soldiers followed the money and supplies: approximately two million Americans had reached Europe by late 1918.

Hunger after the armistice. The blockade continued after the November 1918 armistice, through the winter of 1918–19, and gave the Allies leverage in peace negotiations. Hunger and the imposed peace became connected grievances in German memory. Later Nazi plans for self-sufficiency and the conquest of grain-producing lands drew in part on fear of another blockade. The political consequences of the weapon outlasted the fighting.

The questions left by sea war. Prize law, submarine attacks and restrictions on food had all become urgent questions during the sea war. They returned in the next world war. Several major navies used unrestricted submarine warfare during 1939–45, although their policies and starting dates differed. The experience of 1914–18 had not settled the treatment of merchant crews or civilian supplies in a future war.