Complex sentence: On 11 December the unit carried out a bomb attack on the Long Bar of the Naval and Military Club in Piccadilly, a few minutes later other members of the unit carried out a gun attack on the Cavalry Club, nobody was injured in either attack.
Split into simpler sentences: On 11 December, the unit carried out a bomb attack on the Long Bar of the Naval and Military Club in Piccadilly. A few minutes later, other members of the unit carried out a gun attack on the Cavalry Club, nobody was injured in either attack.