mar 13, 1916 - Germany Agrees to Sussex Pledge regarding U-boat Activity
German Government pledged to the US that they would stop indiscriminately sinking non-military ships with their submarines.
This pledge helped discourage America from joining the war because one of our concerns was the killing of civilians; now that Germany had vowed not to, America had less of a reason to get involved
Added to timeline:
World War 1 - US History