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.

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.

Lieutenant Colonel 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.
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.
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.
Lieutenant Colonel 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.
Battles of Lexington and Concord