Without heavy guns, proper siege equipment or the time and inclination to simply wait the defenders out, MacColla decided to take Mingary castle by assault. Mingary was essentially a thirteenth century castle with high curtain walls and no modern 17th century enhancements such as earthen ramparts or exterior strong point to slow down and break up an attack. With even one heavy gun and a few days time, a portion of the wall might have been reduced to rubble and the resulting breach allow MacColla’s vastly superior force access to the hapless defenders. With this option off the table the wall would have to be scaled at multiple points (an exceedingly difficult and bloody task) OR some other means of entrance found. Mingary does have two gates that allow passage into the interior. On the seaward side was a small gate used for access to boats but the significant word here is small. It would be difficult to get sufficient force through such a narrow gate to assure a quick end to resistance. To the landward side was the main gate which was approached from the mainland by crossing a ditch. No walk in the park either but still the best chance of get the most force into the castle quickly.
The problem now resolved to how to breach the main gate. The typical method was to use a petard (basically a very heavy, metal bell-shaped device packed with gunpowder) that could be wedged against the gate and detonated by fuse. Not having a petard or the specialist adept in its preparation, placement, and firing, MacColla had to resort to the medieval method – stack a large pile of combustibles against the gate and burn it down! To this end the Irish troops raided the countryside for house timbers, furniture, cartwheels, etc until sufficient material for a substantial bonfire was collected. Now came the difficult part – getting all that stuff against the gate and ignited. Presumably MacColla used a large number of musketeers to give what would now be called suppressing fire to keep the defenders from freely interfering with his assault team.
This group carried all the flammable materials to the door and ignited the fire. The Irish suffered somewhere on the order of ten to twenty casualties in the overall assaults on both Kinlochaline and Mingary – logically the majority came from those who fired the door gate at Mingary. It took nearly three hours before a raging fire was going and the attackers could wait for results. The defenders poured barrels of ale over the wall (they were likely short of water) in an attempt to quench the flames but to little avail. The assault began on July 13, 1644 and its length is unclear –possibly only a few hours were required for the garrison to surrender but it could have taken most of a day or a little more. Certainly by the 15th Mingary was firmly in MacColla’s hands.
(David Stevenson give the most detailed information that I could find on the fall of Mingary in his book, Highland Warrior listed on my library page)