Isaac's Revolutionary War service was recalled by his widow Abihail in 1836 in a pension application as follows:

"Isaac entered the army of the revolution, as a private soldier soon after the battle of Lexington...on or about the 20th day of April, in the year 1775, & marched to Marshfield, in the county of Plymouth, & remained there about ten days.  He then returned to his home which was then a part of Bridgewater, now West Bridgewater, & in a few days enlisted for eight months & was appointed a Sergeant in the company commanded by her father, Capt. Daniel Lothrop.  He then marched to Roxbury with that company, was there during the battle of Bunker Hill, & served out his term of eight months. 

"He was employed in recruiting soldiers during the winter of 1775 & 1776, & in the month of April, in the last mentioned year, soon after the Regulars, or British soldiers left Boston, he enlisted into a company of Artillery, under the aforesaid Capt. Daniel Lothrop & Col. Revere, was appointed a Sergeant therein, & went to Noddle's Island, in Boston harbor, & served there about two months, when he received a commission as a Lieutenant in the Continental Army, & served as such under Capt. Stetson & Col. Gamaliel Bradford, until sometime in the month of December, 1777, which last mentioned service was about...eighteen months, at the end of which time he was permitted to resign, at his own request, on account of his ill health, & received a written discharge, which she has seen, under the hand of Gen. Washington. 

"The said commission & discharge were used in preparing the papers to procure the said Isaac Hartwell's pension about the year 1818.  They were carried to Boston, with other papers, at that time, & whether they were left there & lost, or sent to Washington, she does not know.  After he was appointed a Lieutenant he left Noddle's Island, & served as a recruiting officer, in the State of Massachusetts & in the then District of Maine, until he was called to join the Army, when he went to Saratoga, which was only a month or six weeks before the battle at that place, & was engaged therein, before the surrender of Burgoyne.  He then went to White Plains, at which place he received his discharge before mentioned. 

"He then came to Bridgewater & soon after went to Rhode Island, as a substitute for Lieut. Elijah Snell, & served as a Lieutenant for the further time of three months, under Capt. Abram Washburn & Col. Sprout's battalion, as by the old certificate hereunto annexed will appear, making the time in which he served as a Lieutenant, in the whole, twenty-one months, in addition to the time in which he served as a Sergeant.  She is enabled to state the facts herein contained with much confidence, from the circumstances that she, during the whole of the revolutionary war & during the whole of her life, thus far, has resided in the same town with the said Isaac Hartwell, when he was at home, was particularly acquainted with him when he first entered the army, & was married to him during the time he was connected therewith, & before the last term of his service expired...

"She further declares that she was married to the said Isaac Hartwell on the 1st day of February, in the year 1776; that her husband, the aforesaid Isaac Hartwell died on the 12th day of June, in the year 1831; and that she has remained a widow ever since that period."

As noted above, Isaac married the daughter of his commanding officer, Capt. Daniel Lothrop.  A fellow soldier recalled that, during their service in Roxbury, the men in the company were well aware that Isaac and Capt. Lothrop were both from Bridgewater and that Isaac was acquainted with the Captain's daughter.  According to the soldier, Isaac "occasionally went home & the young men used to laugh at him for going a courting."

A genealogy of the Hartwell family published in 1887 states that Isaac was a millwright and "built the old Boston milldam, enclosing what is now the Back Bay, also Milton Mills."  I have not been able to find a primary source to confirm this.

In 1855, Congress passed a law entitling Revolutionary War widows to claim 160 acres of "bounty land."  Abihail applied and her application was approved.  She died in 1857 at age 98, but a warrant (deed) was "signed" in 1863 by Abraham Lincoln granting her land near Pottawatomie Creek in eastern Kansas.  It was typical for recipients of bounty land to sell it rather than occupy it.  It appears that this land was sold by Abihail's son and eventually bought by authorities of the nearby town of Garnett.  Pottawatomie Creek had actually become famous in 1856 as the site of a massacre in which a band of anti-slavery settlers led by abolitionist John Brown killed five pro-slavery settlers.  The Civil War was foreshadowed by a dispute over whether Kansas would be granted statehood as a free state or a slave state.

The whole bounty land saga seems somewhat dubious--a way to attract people to "settle" a western frontier that doesn't sound that attractive to me--a land torn by conflicts over slavery and over the displacement of indigenous natives by incoming settlers.  Of course Abihail never had any intention of heading to Kansas, but this unlikely connection speaks to the times in which she lived.

Fortunately for me, all of the various pension and bounty land applications submitted by Isaac and Abihail were collected in one file, saved by the U.S. government, microfilmed, and eventually made available on the Internet, providing me with a trove of documents that provide a glimpse into the lives of these ancestors.