On 10th May 1777, they both fought in the American raid on their encampment, where John McGregor (Snr) was killed. John McGregor (Jnr) continued fighting until 1783, when he was shipped to Nova Scotia. In 1784, northern Nova Scotia became the new Colony of New Brunswick. So John and 14,000 other Loyalists including the 1st Company of the Black Watch and 14 remnants of British American regiments, arrived in the wilderness of Nashwaak, NB. His Company elected to settle in Nashwaak, where each 42nd Regiment veteran was alloted lots. He married Mary MacMillan in Granville, Nova Scotia in 1793 and started a family which eventually would number 13 surviving children.

These soldier/settlers formed a militia that was tasked with defending the new colony against an expected American encroachment.  John was released from miltary duty in 1803, when his company was disbanded.

After many early hardships, he prospered there.  In 1791, Upper Canada was declared a separate Crown Colony and later, in 1806,  when vast tracts of land around the Sandwich area (later Windsor) were opened up, he decided to take his family there, where he was awarded 200 acres of forested land.  He joined the newly created Kent Riflemen Militia Unit in 1810 as a Sergeant, when it appeared inevitbale that the United Sates would attack Upper Canada. .  Sgt. MacGregor was so impressed with Gen. Sir Isaac Brock that he named his next son after him.

In early 1812, when the second US war erupted, a sizeable army marched north from Kentucky towards Upper Canada.  When General Sir Isaac Brock took Detroit without firing a shot, John MacGregor was there as a Sergeant.  With the critical help of Indian Chiefs, Wyandotte and Tecumseh, the British Army and  Canadian Militias harassed the American militias in Michigan territory and delayed their advance towrds Detroit.nbsp; As a result, many Kentucky militiamen refused to fight in Upper Canada, as their legal terms of service forbade such an (outside of the U.S.) encounter.

By May of 1813, the British regulars had enough in Michigan, with their most aggressive leader, Gen. Brock dead, and under the inept leadership of Col. Proctor, they retreated back into Upper Canada.  

Sergeant MacGregor fought at the disastrous battle of Moraviantown, which left the Americans occupying a large tract of south-western Upper Canada for the duration of the war.  (This loss of territoryHalifax in Sepember of 1814 Nova Scotia, plus later seizures of several US forts in Michigan Territory and New York).

The Kent Militia went underground, and Lieut. John MacGregor was their leader.  His guerrilla tactics in several skirmishes with the Americans, including the Battle of Longwoods earned him recognition as a brilliant leader and a tough taskmaster.

MacGregor's guerillas had been fighting and surviving in the wilderness for an entire winter.  In the battle of Longwoods, in late February of 1814, he fought against superior odds, in spite of the stubbornness of senior British officers and their contempt for colonial militias, to send the American forces reeling back to Detroit.  He lost an arm in an action where he led a rearguard attack to save threatened British regular Army troops from disaster.  For this gallant action, he was awarded his Captaincy.

Renamed by John MacGregor, the "Loyal Kent Volunteers", succeeded in harassing American forces in Michigan and northern Ohio.    MacGregor and his militia were given all the difficult travel assignments, roaming the entire area with their Indian comrades, at will, daring the Americans to put up a fight.

After the war came to a close, Captain John MacGregor wrote many petitions on behalf of his men.  Subsequently, medals were awarded, with considerable monetary and property awards processed.  In recognition of  his services, He was awarded more than 850 acres, comprising what is now the southern half of the city of Wallaceburg.