When darkness fell on April 19 - a date still observed as "Patriots Day", a State holiday in Massachusetts - General Gage's troops were safely back in their Boston enclave, but they were effectively bottled up there by an ad hoc army of militiamen just across Boston Neck. These militiamen had been called up for only short term service, and most of them would be discharged to return home by late April or early May. Accordingly, the Massachusetts Provincial Congress, a revolutionary legislature meeting in Watertown which was the de facto government for all of Massachusetts outside British-controlled Boston, sprung into action. On April 23, this body authorized the formation of a number of regiments of State troops to constitute a 13,600 man "Army of Observation", to "observe" the British garrison in Boston. Still professing to be loyal subjects of the Crown, the provincial congressmen could not bring themselves to use the more confrontational, military term "besiege", although a siege is nevertheless what they effectively undertook.

As the militiamen who had responded to the "Lexington Alarm" gradually dispersed, they were replaced by these new, somewhat more permanent regiments, most of the officers and men of which were enlisted to serve until the end of the year. Within a month, the "Army of Observation" grew to well over 12,000 men, plus officers, in some 24 regiments of Massachusetts Troops, and 3 regiments each of Connecticut, New Hampshire, and Rhode Island Troops, under the overall command of Massachusetts Major General Artemas Ward. These troops were in no sense of the term "professional" soldiers, but all of them had received at least a modicum of military training through their local militia units at home, and many of their officers were veterans of the French and Indian War. They were more than adequate to contain Gage's 3,000 Redcoats, and on June 14 they were "adopted" by the Continental Congress meeting in Philadelphia as the Continental Army, America's first national army. The congressmen in Philadelphia appointed one of their own members, George Washington of Virginia, to command the army, with the rank of lieutenant general.

However, significant events would transpire before General Washington could receive his commission and travel to Cambridge to assume his command. On May 25, Major Generals William Howe, Henry Clinton, and John Burgoyne arrived from England with reinforcements for the beleaguered Gage - bringing British troop strength up to about 6,500 men - and orders to establish martial law in the rebellious colony. Deciding that they needed some "elbowroom" in Burgoyne's famous phrase, the British generals planned to seize Dorchester Heights, Roxbury, Charlestown, and Cambridge in a four-pronged attack scheduled for June 18. Ever vigilant Boston Patriots got wind of the plan, and promptly passed it along to General Ward and the Provincial Congress. Adopting a bold course, the colonists determined to preempt the British move by sending a picked force onto the Charlestown Peninsula on the night of June 16-17 to fortify Bunker Hill under cover of darkness, thereby forcing the British to attack them the next day under unfavorable conditions.

Colonel William Prescott commanded three regiments of Massachusetts State Troops assigned to this duty, and directed the erection of an earthwork redoubt on Breed's Hill, buttressed on its left by a breastwork extending about 150 yards to the north. Perhaps 100 yards behind the breastwork, at the foot of Bunker Hill, an existing fence extending down to the bank of the Mystic River was reinforced, and, at the last minute, the line of this fence was extended across the beach to the water's edge by a quickly erected stone barrier. The gap between the left end of the breastwork and the right end of the reinforced fence was covered by the erection of three V-shaped "fleches", points facing outward, while the right flank of the redoubt was covered by several companies of troops stationed as snipers in Charlestown and several buildings to the west overlooking the Charles River. At one time or another, as Prescott's initial detachment was gradually reinforced, well over 2,000 troops manned the Patriot line, but many of the men originally sent to fortify the position were exhausted from their work and withdrew as reinforcements arrived. Hence, there were not more than 1,500 men in position when the British attacked.

When the sun came up on June 17, the British were astounded at the work the provincials had done during the night. They quickly resolved to capture or destroy the forces dug in on Breed's Hill and then directly march into Cambridge and break up the "Army of Observation". General Howe was placed in command of the operation with about 2,500 men. His plan was to stage amphibious landings at Moulton's Point and just north of Charlestown, and then attack the colonists' position frontally while simultaneously turning its left flank in a dash by the light infantry up the Mystic River beach. However, the colorful Colonel John ("live free or die") Stark and his New Hampshire troops, who erected the stone barrier across the Mystic River beach shortly before the British attack, thwarted the flanking maneuver and inflicted frightful casualties on the light infantry. Meanwhile, Patriot defenders who held their fire "until they could see the whites of the attackers' eyes" repulsed the frontal assault with heavy losses. A second frontal assault all along the line was also bloodily repulsed. Not to be denied, and reinforced by a fresh regiment of infantry and battalion of marines ferried over from Boston, the British came on yet a third time. The Patriots now ran out of powder and shot, and abandoned their position rather than face British bayonets with nothing but empty muskets. But the Redcoats, having lost 226 officers and men killed and 828 wounded - almost half their force - were too weak to give pursuit. American losses were 145 killed and 304 wounded.

While the Battle of Bunker Hill was a tactical victory for the British, it did little to alter the strategic situation. Burgoyne's "elbowroom" on the Charlestown Peninsula had been acquired at a prohibitive cost. "I'd like to sell them another hill at the same price", an American officer observed; "one more such victory and we shall be undone", noted a Redcoat. The British remained effectively bottled up on two small peninsulas in Boston harbor, dependant upon the sea for supplies. The Patriots tightened their siege lines, and reorganized their forces upon the arrival of General Washington on July 3. They slowly began to acquire more of a military aspect, and although most of their enlistments expired at the end of the year many re-enlisted, and the positions of those who didn't were quickly filled with new volunteers. Over the winter, cannon captured from the British at Fort Ticonderoga on Lake Champlain were transported by sled to Boston by Colonel (later General) Henry Knox, and emplaced on Dorchester Heights so as to command Boston and render it untenable. The British, now under command of General Howe since Gage's return to England, were forced to evacuate the city on March 17, 1776, and sail to Halifax to regroup. To this day, March 17 is celebrated in Boston not only as St. Patrick's Day, but also as Evacuation Day.

As near as can be determined from Massachusetts records, the following Stebbins served in the Patriot cause during the Siege of Boston:

          Colonel David Brewer's (later Lt. Col. Rufus Putnam's) Regiment

               Captain Jonathan Bardwell's Company

                    Abraham Stebbens (also spelled "Stebbings" and "Stebeons"), Ware.
                    Enlisted May 3, 1775; served 3 months, 5 days.

               Captain Isaac Colton's Company

                    Luke Stebbins, Kensington.  Listed on muster rolls at Camp Roxbury,
                    October 7, 1775 and November 7, 1775.

          Colonel Jonathan Ward's Regiment

               Captain Eliakim Smith's (later Captain Moses Kellogg's) Company

                    Corporal Asahel Stebbins, Northfield.  Enlisted June 1, 1775; 
                    served 2 months, 5 days.

                    Cyrus Stebbins, Northfield.  Enlisted April 27, 1775;
                    served 3 months, 12 days.

          Colonel Timothy Danielson's Regiment

               Captain Joseph Thompson's Company

                    Hezediah Stebbins (also spelled "Stebbens"), Brimfield.

               Captain Paul Langdon's Company

                    Aaron Stebbins, Wilbraham.  Enlisted April 29, 1775;
                    served 3 months, 1 week, 3 days.

          Colonel Ebenezer Learned's Regiment

               Captain Thomas Stebbins (also spelled "Stebbing"), Springfield.
               Commanded a company of 68 men raised in Springfield, West Springfield,
               And Wilbraham; served until the end of January, 1776.

          Colonel Jonathan Brewer's Regiment

               Captain Joseph Stebbins, Deerfield.  Commission delayed because his company 
               had only 21 men as of June 17, 1775 (at the Battle of Bunker Hill).