Complex sentence: Some 15,000 troops under Howe's command sailed from New York on 23 July and landed at Head of Elk (now Elkton), Maryland, a month later (25 August).
Split into simpler sentences: Some 15,000 troops under Howe's command sailed from New York on 23 July and landed at Head of Elk. Maryland (now Elkton, Maryland), a month later (25 August).