Battle of Glen Fruin The Battle of Glen Fruin was fought on February 9 , 1603 between the Clan Gregor and its allies on one side , and the Clan Colquhoun and its allies on the other . Glen Fruin is located in the Loch Lomond area , in the county of Dunbartonshire , Scotland . Lead up to the Battle . According to the Clan Gregor ; two MacGregor clansmen , away from home , were forced to spend a night in Colquhoun lands . After being refused shelter , the two MacGregors found an abandoned outhouse and slaughtered a sheep which they ate . When the two were discovered they were seized and brought forward to Colquhoun , the Laird of Luss . Sir Humphrey Colquhoun of Luss , chief of the Clan Colquhoun , had the men tried by summary trial then sentenced the men to death . To avenge the two slain clansmen , the chief of Clan Gregor , Alasdair MacGregor of Glenstrae , led 300 to 400 men under his command with the help of Macfarlanes , from the banks of Loch Long , by way of the " " Raid na Gael " " ( Scottish Gaelic ) , " Highlandman ' s Pass " , towards the Colquhoun lands of Luss . The Laird of Luss , gaining early notice of the MacGregors , gathered nearly twice the number of the invaders . Among them were Buchanans , Grahams , and men from the surrounding Lennox district . The conflict at Glen Fruin . As the two sides converged in the lands of Glen Fruin , the MacGregor led force was at first discouraged by the superior size of the Colquhoun led contingent . It is said a Seer encouraged the MacGregors , saying he saw the " shrouds of the dead wrapt " around their opponents . The main contingent of the MacGregor force attacked their enemies head on , while a force flanked the Colquhouns , led by Iain Dubh MacGregor , brother of the chief . The Colquhoun ' s advantage of having a large number of cavalry present turned into a disadvantage by boggy ground of the glen , and the MacGregors pressed on to rout the Colqhouns and their allies . Tradition is that the MacGregors had only very light casualties , though among them was Iain Dubh . The Colquhoun force lost between 200 to 300 men . Alleged slaughter of students . A tradition grew that a group of clerical students from the town of Dumbarton , who had assembled to watch the battle , were slaughtered by the MacGregors during the rout of the Colquhouns . It is remarked by historians that this alleged slaughter is curiously not part of the indictment against the chief of the MacGregors . Though the event seems to have been entwined in lore of the surrounding area and also part of MacGregor lore . The location of the deed is marked by " " Leac a ' Mhinisteir " " ( Scottish Gaelic ) , " Minister " or " Clerk ' s Flag - stone " . According to MacGregor tradition , the man who committed the deed was Dugald Ciar Mhor , ( " Dugald the great , mouse coloured " ) , a foster brother of the chief , who was renowned for his great size and strength . It was amidst the battle that the chief entrusted the youths to Dugald ' s protection , with directions to keep them fleeing . For reasons unknown , possibly for fear of their escape or of some injustice to him or his clan , Dugald slaughtered the defenceless students . When the chief , Alasdair , demanded where the youths were Dugald is said to have drawn his bloody dirk saying in gaelic " " Ask that , and God save me ! " "