Boston campaign

It is often said that the American war of Independence began with the British on April 19th, 1775, during Boston siege (battles of Concord and Lexington) but the first event that triggered the popular reaction to english invasion started with what’s known as the Powder Alarm.

On September 1st, 1774, british soldiers confiscated powder supplies and weapons from the militia during a surprise action near Boston. This expedition alarmed the entire country and american patriots ran into action, persuaded war had begun. Even though this alarm was false, it enticed everyone to be more careful.

For more info about the Boston campaign, see Wikipedia.