Complex sentence: The 6th Cavalry left Fort McKinney a few hours later at 2 am on April 13 and reached the TA ranch at 6:45 am as the settlers were about to use the Ark of Safety.
Split into simpler sentences: The 6th Cavalry left Fort McKinney a few hours later at 2 am on April 13 and reached the TA ranch at 6:45 am. As the settlers were about to use the Ark of Safety.