Complex sentence: The Royal Navy of the British military distributed to their sailors Waltham pocket watches, which were 9 jewel movements, with black dials, and numbers coated with radium for visibility in the dark, in anticipation of the eventual D-Day invasion.
Split into simpler sentences: The Royal Navy of the British military distributed to their sailors Waltham pocket watches, which were 9 jewel movements, with black dials, and numbers coated with radium for visibility in the dark. The theory today is that the watches were ordered in anticipation of the eventual D-Day invasion.