Complex sentence: The British and French forces began to land on the Crimean peninsula on 14 September 1854, on 19 September the combined forced moved off toward Sebastopol, and on 20 September came the first major engagement of the campaign, the Battle of the Alma.
Split into simpler sentences: The British and French forces began to land on the Crimean peninsula on 14 September 1854. On 19 September the combined forces moved off toward Sebastopol and on 20 September came the first major engagement of the campaign, the Battle of the Alma.