Final answer:
On April 18, 1775, British troops moved to arrest leaders and seize supplies in Concord, but were met by armed colonial militia in Lexington, and after a skirmish known as the 'shot heard around the world,' were forced to retreat.
Step-by-step explanation:
On the night of April 18, 1775, a pivotal series of events occurred that laid the groundwork for the American Revolutionary War. British troops, having been stationed in Boston, moved out to seize military supplies and arrest revolutionary leaders in Concord. However, the alarm was raised by riders Paul Revere, William Dawes, and others using bonfires, bells, and other signaling means, which allowed the Lexington militia and other volunteers to assemble in preparation. The early morning of April 19 saw these colonial militias face the advancing British forces at Lexington Green, resulting in a skirmish that left eight colonists dead. Infamous as the "shot heard around the world", the first battle of the Revolutionary War continued at the North Bridge in Concord where the British were met by organized resistance and forced to retreat, facing gunfire from the colonists along their return to Boston. This confrontation sparked the full-blown war for independence, with the Second Continental Congress eventually establishing the Continental Army and appointing George Washington as its commander.