Complex sentence: He strongly opposed, but was unable to prevent, the expedition into England, and in the subsequent reduction of Scotland, after having held out in Inveraray Castle for nearly a year, was at last surprised in August 1652 and submitted to the Commonwealth.
Split into simpler sentences: He strongly opposed, but was unable to prevent, the expedition into England. In the subsequent reduction of Scotland, after holding out in Inveraray Castle for nearly a year, he was at last surprised in August 1652 and submitted to the Commonwealth.