Complex sentence: Following the defeat in Preston, Grimshaw emigrated to the United States, where he became a supporter of the Confederacy and upon his return to the United Kingdom he joined a small group of Lancashire men who unsuccessfully attempted to rally support for the Confederates in northern England.
Split into simpler sentences: Following the defeat in Preston, Grimshaw emigrated to the United States, where he became a supporter of the Confederacy. The following year he joined a small group of Lancashire men who unsuccessfully attempted to rally support for the Confederates in northern England.