Complex sentence: The advance cruisers of the German squadron had been detected early on, by nine o'clock that morning the British battlecruisers and cruisers were in hot pursuit of the five German vessels, these having taken flight in line abreast to the southeast.
Split into simpler sentences: The advance cruisers of the German squadron had been detected early on. By nine o'clock that morning the British battlecruisers and cruisers were in hot pursuit of the five German vessels, these having taken flight in line abreast to the southeast.