The war soon struck vast numbers of Europeans in more deadly fashion. The range of modem military forces and new weapons made civilians the direct targets of military action. In December 1914, for example, the German navy slipped past British defenses in the North Sea and bombarded three towns along the Yorkshire coast. In Hartlepool, Scarborough, and Whitby more than 100 civilians died and 600 were wounded. German Zeppelins began to strike southeastern England in January 1915; they bombed London in May and eventually reached much of the southern half of the country. This World War I version of "the Battle of Britain" was a preview of the greater aerial struggle that began a quarter century later. In 1917 the Germans began to rely mainly on bombing planes. Their entire aerial assault on Britain caused about 1,500 deaths and 3,400 injuries between 1915 and the close of the war. Paris, too, fell victim to a range of enemy assaults. The Zeppelins appeared in March 1915 and again in 1916, and enemy bomber attacks, notably in the first eight months of 1918, caused hundreds of casualties. In March 1918, the German army began to use massive naval guns to shell France's capital from the northeast. Fired at a distance of seventy-five miles, the shells struck at random at the city's civilian population for forty-four days. Two hundred fifty-six Parisians died and 625 were wounded, with shells landing on churches and in the lovely city's main squares. On the other side, in 1917 and 1918, British and French bombers made numerous raids on the cities of western Germany—Mainz, Cologne, Karlsruhe, and Trier—hitting as far eastward as Stuttgart. More than 700 Germans were killed and more than 1,800 injured in these attacks. Civilians died as well at their newly dangerous workplaces. In December 1916, for example, thirty-five women munitions workers in Britain were killed in an accident in a plant near Leeds; in January 1918, a worse catastrophe killed sixty-nine workers and injured hundreds more when their factory in East London exploded. Starting in October 1914, German submarines began their attacks on Allied merchant ships. They were soon, deliberately or by accident, sinking neutral vessels as well. Allied submarines sank German vessels in the Baltic, but the German attacks in the Atlantic and the Mediterranean shaped the reaction to this novel form of warfare. The civilian passengers and seamen who died on torpedoed ocean liners and merchant ships—3,000 Norwegian seamen among them—were the most significant noncombatant casualtiesof the war. Such deaths pulled the neutral United States first to the brink of war, then into the maelstrom.