Complex sentence: B-7 Escort Group (B-7 EG) was one of seven British escort groups which served with the Mid-Ocean Escort Force (MOEF), which provided convoy protection in the most dangerous midsection of the North Atlantic route.
Split into simpler sentences: B-7 Escort Group (B-7 EG) was one of seven such British naval groups which served with the Mid-Ocean Escort Force (MOEF). It provided convoy protection in the most dangerous midsection of the North Atlantic route.