Complex sentence: The Elswick Ordnance Works was the Armstrong Whitworth armaments branch and major arms developer in World War I. It was absorbed into the Armstrong Whitworth umbrella, but writers commonly refer to Elswick Ordnance as the armaments developer.
Split into simpler sentences: The Elswick Ordnance Works was the Armstrong Whitworth armaments branch. It came under the Armstrong Whitworth umbrella, but writers commonly refer to Elswick Ordnance as the armaments developer.