 Not long after assuming the chiefship , Lachlan Og was forced to resign some of his lands to the chief of the Lamonts , because of the murder of Robert Lamont of Silvercrags by Lachlan Maclachlan of Dunnamuch . Lachlan Og led the clan in the Archibald Campbell , 7th Earl of Argyll 's campaign against Sir James Macdonald of Islay and his rebellion in 1615 . 
