Complex sentence: On 1 May 1915 near Hill 60, Ypres, Belgium, when a trench had been vacated by British troops after a gas attack, Private Warner entered it alone in order to prevent the enemy taking possession.
Split into simpler sentences: On 1 May 1915 near Hill 60, Ypres, Belgium, a trench had been vacated by British troops after a gas attack. Acting alone, Private Warner entered it in order to prevent the enemy taking possession.