Thousands of militiamen began streaming toward Boston and Cambridge, and mob action forced Loyalists and some government officials to flee to the protection of the British Army.

"[3] General Thomas Gage, who had become the military governor of Massachusetts in May 1774, was charged with enforcement of the highly unpopular Intolerable Acts, which British Parliament had passed in response to the Boston Tea Party.

Seeking to prevent the outbreak of war and to keep the peace between the American Patriot (Whig) majority and the Loyalist (Tory) minority, he believed that the best way to accomplish this was by secretly removing military supplies from storehouses and arsenals in New England.

One locked storehouse near Boston, in what was then part of Charlestown, now Powder House Square in Somerville, was controlled by William Brattle, the leader of the provincial militia and an appointee of the governor.

Brattle, who had not obviously sided with either Loyalists or Patriots, notified Governor Gage in a letter dated August 27 that the provincial ("King's") powder was the only supply remaining in that storehouse, as the towns had removed all of theirs.

[9] At some point that day, General Gage, whether by his intent, accident, or theft by a messenger, lost possession of the August 27 letter from William Brattle; the widely held story is that it was dropped.

[10] Early in the morning of September 1, a force of roughly 260 British regulars from the 4th Regiment, under the command of Lieutenant Colonel George Maddison, was rowed in secrecy up the Mystic River from Boston to a landing point near Winter Hill in modern-day Somerville.

[12] On September 2, several thousand men bent on violence gathered in Cambridge, where they forced several notable Loyalists, including William Brattle, to flee to Boston and the protection of the military.

If it had proved true, you would have heard the thunder of an American Congress.Gage, surprised by the size and scope of the colonial reaction, delayed and eventually cancelled a second planned expedition to the storehouse in Worcester.

[17] He concentrated his troops in Boston, and called for reinforcements from London, writing "if you think ten thousand men sufficient, send twenty; if one million is thought enough, give two; you save both blood and treasure in the end.

[16] After the Powder Alarm, militia forces throughout New England were more cautious with their supplies and more intent on gaining information about Gage's plans and troop movements.

[20] On September 21, Patriot leaders met in Worcester and urged town meetings to organize a third of the militias into special companies of minutemen in constant readiness to march.

[22] Early in December 1774, British military command voted to prohibit the export of arms and powder to North America and to secure all remaining stores.

[24] On February 27, 1775, HMS Lively brought a force of about 240 British regulars from the 64th Regiment under Colonel Alexander Leslie to confiscate weapons in Salem, Massachusetts.