 
freedom of the seas was a long-standing principle of international law, 
and the united states stoutly defended it. 
under the laws of war, a neutral nation has the right to trade with 
warring nations, as long as it trades with both sides in the conflict. 
yet, just as during the napoleonic wars, enjoyment of freedom of the seas 
during wartime was difficult. 
britain could not allow the united states to ship war supplies to germany. 
nor could the germans permit shipments to great britain. 
both sides repeatedly interfered with american ships. 
but there were important differences between the opposing sides. 
american businessmen were making huge profits out of a greatly increased 
trade with britain and very little from the german trade. 
also, the british seized rather than sank american ships bound for 
germany. 
they even paid good prices for the captured goods. 
besides, britain and france were democracies. 
in addition, the germans started a murderous submarine warfare. 
the early submarine was a fragile underwater ship that could easily be 
sunk by a light artillery gun. 
it relied on surprise hit-and-run attacks. 
early in the war, without giving warning, a german submarine torpedoed the 
lusitania, a large, unarmed british passenger liner. 
some 1,200 men, women, and children died, including 128 americans. 
deeds such as this shocked the nation. 
repeatedly president wilson sent strong letters of protest to the germans 
over submarine warfare. 
gradually the majority of the american people came to hate the german 
kaiser (emperor) and his autocratic government. 
the kaiser was cartooned as the ugly, bloodthirsty "beast of berlin." 
