With a total of almost six years in a combat theater between two wars, by 1953 Major McNabb had only seen about thirty-seven days in combat conditions.  The first seventeen days were spent with the provisional Beauman Division - his battalion was improvised from 1st Line Reinforcements from the 51st Highland Division during the retreat and defense of Dunkirk.  He was captured on June 9th, 1940 at a dusty road junction and marched off to rail cars for transport across Europe.  

Until liberated in April 1945, he spent time in six different camps during which time he was a menace to the German.  His first escape attempt was on the train from Posen, which was a short lived success before rounded up again.  He was member of an escape committee for eighteen months, tasked with creating escape maps which were very successful for those who used them, however McNabb himself was never able to evade his captors and was caught several times trying to break out.  The most successful of which was a tunnel system that took weeks to construct with other members of the camp known as 'the Worms.'

When the Royal Scots arrived in the Korean theater on July 7, 1953 McNabb went with the advanced party to the positions of the Black Watch.  The group organized relief of their sister Scottish regiment and in two days the rest of the Scots joined then and McNabb resumed his role B Company’s second in command.  Training and exercises consumed the next twenty days for the Scots, and though the armistice declaration on July 27 officially ended the war, it did not change the way of life in trenches or the necessary patrolling along the line to ensure the Chinese were keeping their distance.

By 1958, McNabb had transitioned to the roles of a staff officer with the Northern Ireland Command and was handling the organization of the Territorial Army Jubilee Review as well as the Reception for Her Majesty Queen Elizabeth.  He worked closely with the government and police forces of Northern Ireland and his experience and connections were of great benefit a decade later when he worked on improving the accommodations and well-being of soldiers serving in the Northern Ireland Emergency.  The short-lived problems only had such an appearance due to how rapidly McNabb tackled these issues.