British Army's infantry was nicknamed "
redcoats" and sometimes "devils" by the colonists. They had
occupied Boston since 1768 and had been augmented by
naval forces and
marines to enforce what the colonists called The
Intolerable Acts, which had been passed by the
British Parliament to punish the
Province of Massachusetts Bay for the
Boston Tea Party and other acts of defiance.
Thomas Gage was the military
governor of Massachusetts and commander-in-chief of the roughly 3,000 British military forces garrisoned in Boston. He had no control over Massachusetts outside of Boston, however, where implementation of the Acts had increased tensions between the Patriot
Whig majority and the pro-British
Tory minority. Gage's plan was to avoid conflict by removing military supplies from Whig militias using small, secret, and rapid strikes. This struggle for supplies led to one British success and several Patriot successes in a series of nearly bloodless conflicts known as the
Powder Alarms. Gage considered himself to be a friend of liberty and attempted to separate his duties as governor of the colony and as general of an occupying force.
Edmund Burke described Gage's conflicted relationship with Massachusetts by saying in Parliament, "An Englishman is the unfittest person on Earth to argue another Englishman into slavery."
The colonists had been forming militias since the very beginnings of Colonial settlement for the purpose of defense against
Indian attacks. These forces also saw action in the
French and Indian War between 1754 and 1763 when they fought alongside British regulars. Under the laws of each New England colony, all towns were obligated to form militia companies composed of all males 16 years of age and older (there were exemptions for some categories), and to ensure that the members were properly armed. The Massachusetts militias were formally under the jurisdiction of the provincial government, but militia companies throughout New England elected their own officers.
 Gage effectively dissolved the provincial government under the terms of the
Massachusetts Government Act, and these existing connections were employed by the colonists under the
Massachusetts Provincial Congress for the purpose of resistance to the military threat from Britain.
British government preparations
A February 1775 address to
King George III, by both houses of Parliament, declared that a state of rebellion existed:
We ... find that a part of your Majesty' s subjects, in the Province of the Massachusetts Bay, have proceeded so far to resist the authority of the supreme Legislature, that a rebellion at this time actually exists within the said Province; and we see, with the utmost concern, that they have been countenanced and encouraged by unlawful combinations and engagements entered into by your Majesty's subjects in several of the other Colonies, to the injury and oppression of many of their innocent fellow-subjects, resident within the Kingdom of Great Britain, and the rest of your Majesty' s Dominions ....
We ... shall ... pay attention and regard to any real grievances ... laid before us; and whenever any of the Colonies shall make a proper application to us, we shall be ready to afford them every just and reasonable indulgence. At the same time we ... beseech your Majesty that you will ... enforce due obedience to the laws and authority of the supreme Legislature; and ... it is our fixed resolution, at the hazard of our lives and properties, to stand by your Majesty against all rebellious attempts in the maintenance of the just rights of your Majesty, and the two Houses of Parliament.
On April 14, 1775, Gage received instructions from
Secretary of State
William Legge, Earl of Dartmouth, to disarm the rebels and to imprison the rebellion's leaders, but Dartmouth gave Gage considerable discretion in his commands.
 Gage's decision to act promptly may have been influenced by information he received on April 15, from a spy within the Provincial Congress, telling him that although the Congress was still divided on the need for armed resistance, delegates were being sent to the other New England colonies to see if they would cooperate in raising a New England army of 18,000 colonial soldiers.
, commander of the military expedition, in a 1763 portrait
On the morning of April 18, Gage ordered a mounted patrol of about 20 men under the command of Major Mitchell of the
5th Regiment of Foot into the surrounding country to intercept messengers who might be out on horseback.
 This patrol behaved differently from patrols sent out from Boston in the past, staying out after dark and asking travelers about the location of
Samuel Adams and
John Hancock. This had the unintended effect of alarming many residents and increasing their preparedness. The Lexington militia in particular began to muster early that evening, hours before receiving any word from Boston. A well-known story alleges that after nightfall one farmer, Josiah Nelson, mistook the British patrol for the colonists and asked them, "Have you heard anything about when the regulars are coming out?" upon which he was slashed on his scalp with a sword. However, the story of this incident was not published until over a century later, which suggests that it may be little more than a family myth.
Francis Smith received orders from Gage on the afternoon of April 18 with instructions that he was not to read them until his troops were underway. He was to proceed from Boston "with utmost expedition and secrecy to Concord, where you will seize and destroy ... all Military stores ... But you will take care that the soldiers do not plunder the inhabitants or hurt private property." Gage used his discretion and did not issue written orders for the arrest of rebel leaders, as he feared doing so might spark an uprising.
On March 30, 1775, the Massachusetts Provincial Congress issued the following resolution:
Whenever the army under command of General Gage, or any part thereof to the number of five hundred, shall march out of the town of Boston, with artillery and baggage, it ought to be deemed a design to carry into execution by force the late acts of Parliament, the attempting of which, by the resolve of the late honourable
Continental Congress, ought to be opposed; and therefore the military force of the Province ought to be assembled, and an army of observation immediately formed, to act solely on the defensive so long as it can be justified on the principles of reason and self-preservation.
The rebellion's leaders—with the exception of
Paul Revere and
Joseph Warren—had all left Boston by April 8. They had received word of Dartmouth's secret instructions to General Gage from sources in
London well before they reached Gage himself.
 Adams and Hancock had fled Boston to the
home of one of Hancock's relatives in Lexington, where they thought they would be safe from the immediate threat of arrest.
The Massachusetts militias had indeed been gathering a stock of weapons, powder, and supplies at Concord and much further west in
 An expedition from Boston to Concord was widely anticipated. After a large contingent of regulars alarmed the countryside by an expedition from Boston to
Watertown on March 30, The Pennsylvania Journal, a newspaper in Philadelphia, reported, "It was supposed they were going to Concord, where the Provincial Congress is now sitting. A quantity of provisions and warlike stores are lodged there .... It is ... said they are intending to go out again soon.
On April 8, Paul Revere rode to Concord to warn the inhabitants that the British appeared to be planning an expedition. The townspeople decided to remove the stores and distribute them among other towns nearby.
The colonists were also aware that April 19 would be the date of the expedition, despite Gage's efforts to keep the details hidden from all the British rank and file and even from the officers who would command the mission. There is reasonable speculation, although not proven, that the confidential source of this intelligence was
Margaret Gage, General Gage's
New Jersey-born wife, who had sympathies with the Colonial cause and a friendly relationship with Warren.
Between 9 and 10 pm on the night of April 18, 1775, Joseph Warren told Revere and
William Dawes that the British troops were about to embark in boats from Boston bound for Cambridge and the road to Lexington and Concord. Warren's intelligence suggested that the most likely objectives of the regulars' movements later that night would be the capture of Adams and Hancock. They did not worry about the possibility of regulars marching to Concord, since the supplies at Concord were safe, but they did think their leaders in Lexington were unaware of the potential danger that night. Revere and Dawes were sent out to warn them and to alert colonial militias in nearby towns.
Militia forces assemble
Dawes covered the southern land route by horseback across
Boston Neck and over the
Great Bridge to Lexington.
 Revere first gave instructions to send a signal to Charlestown using lanterns hung in the steeple of Boston's
Old North Church. He then traveled the northern water route, crossing the mouth of the
Charles River by rowboat, slipping past the British warship
HMS Somerset at anchor. Crossings were banned at that hour, but Revere safely landed in Charlestown and rode west to Lexington, warning almost every house along the route.
 Additional riders were sent north from Charlestown.
and several other messengers on horseback sounded the alarm that the regulars were leaving Boston.
After they arrived in Lexington, Revere, Dawes, Hancock, and Adams discussed the situation with the militia assembling there. They believed that the forces leaving the city were too large for the sole task of arresting two men and that Concord was the main target. The Lexington men dispatched riders to the surrounding towns, and Revere and Dawes continued along the road to Concord accompanied by
Samuel Prescott. In
Lincoln, they ran into the British patrol led by Major Mitchell. Revere was captured, Dawes was thrown from his horse, and only Prescott escaped to reach Concord.
 Additional riders were sent out from Concord.
ride of Revere, Dawes, and Prescott triggered a flexible system of "alarm and muster" that had been carefully developed months before, in reaction to the colonists' impotent response to the
Powder Alarm. This system was an improved version of an old notification network for use in times of emergency. The colonists had periodically used it during the early years of Indian wars in the colony, before it fell into disuse in the
French and Indian War. In addition to other express riders delivering messages, bells, drums, alarm guns, bonfires and a trumpet were used for rapid communication from town to town, notifying the rebels in dozens of eastern Massachusetts villages that they should muster their militias because over 500 regulars were leaving Boston. This system was so effective that people in towns 25 miles (40 km) from Boston were aware of the army's movements while they were still unloading boats in Cambridge.
 These early warnings played a crucial role in assembling a sufficient number of colonial militia to inflict heavy damage on the British regulars later in the day. Adams and Hancock were eventually moved to safety, first to what is now
Burlington and later to
British forces advance
Around dusk, General Gage called a meeting of his senior officers at the
Province House. He informed them that instructions from Lord Dartmouth had arrived, ordering him to take action against the colonials. He also told them that the senior colonel of his regiments, Lieutenant Colonel Smith, would command, with Major
John Pitcairn as his executive officer. The meeting adjourned around 8:30 pm, after which Earl Percy mingled with town folk on
Boston Common. According to one account, the discussion among people there turned to the unusual movement of the British soldiers in the town. When Percy questioned one man further, the man replied, "Well, the regulars will miss their aim."
"What aim?" asked Percy. "Why, the cannon at Concord" was the reply.
 Upon hearing this, Percy quickly returned to Province House and relayed this information to General Gage. Stunned, Gage issued orders to prevent messengers from getting out of Boston, but these were too late to prevent Dawes and Revere from leaving.
The British regulars, around 700 infantry, were drawn from 11 of Gage's 13 occupying infantry regiments. Major Pitcairn commanded ten elite
light infantry companies, and Lieutenant Colonel Benjamin Bernard commanded 11
grenadier companies, under the overall command of Lieutenant Colonel Smith.
Of the troops assigned to the expedition, 350 were from grenadier companies drawn from the
59th Regiments of Foot, and the 1st Battalion of
His Majesty's Marine Forces. Protecting the grenadier companies were about 320
light infantry from the 4th, 5th, 10th, 23rd, 38th, 43rd, 47th, 52nd, and 59th Regiments, and the 1st Battalion of the Marines. Each company had its own lieutenant, but the majority of the captains commanding them were volunteers attached to them at the last minute, drawn from all the regiments stationed in Boston. This lack of familiarity between commander and company would cause problems during the battle.
The British began to awaken their troops at 9 pm on the night of April 18 and assembled them on the water's edge on the western end of Boston Common by 10 pm. Colonel Smith was late in arriving, and there was no organized boat-loading operation, resulting in confusion at the staging area. The boats used were naval barges that were packed so tightly that there was no room to sit down. When they disembarked near Phipps Farm in Cambridge, it was into waist-deep water at midnight. After a lengthy halt to unload their gear, the regulars began their 17 miles (27 km) march to Concord at about 2 am.
 During the wait they were provided with extra ammunition, cold
salt pork, and hard
sea biscuits. They did not carry knapsacks, since they would not be encamped. They carried their
haversacks (food bags), canteens, muskets, and accoutrements, and marched off in wet, muddy shoes and soggy uniforms. As they marched through
Menotomy, sounds of the colonial alarms throughout the countryside caused the few officers who were aware of their mission to realize they had lost the element of surprise.
At about 3 am, Colonel Smith sent Major Pitcairn ahead with six companies of light infantry under orders to quick march to Concord. At about 4 am Smith made the wise but belated decision to send a messenger back to Boston asking for reinforcements.