Complex sentence: Iain joined the forces of John Graham, 1st Viscount Dundee and fought at the Battle of Killiecrankie in 1689 and as a result he was denounced as a Jacobite rebel and his remaining lands were forfeited.
Split into simpler sentences: Iain joined the forces of John Graham, 1st Viscount Dundee and fought at the Battle of Killiecrankie in 1689. As a result he was denounced as a Jacobite rebel and his remaining lands were forfeited.