Complex sentence: The patrol saw nothing in the mist but at 05:17 a large of group Ottoman soldiers was seen by a sentry who fired on them which alerted the nearest redoubt garrison of 50 rifles and a Lewis gun which swept the Ottoman ranks.
Split into simpler sentences: The patrol saw nothing in the mist, but at 05:17 a sentry saw a large of group Ottoman soldiers and opened fire on them. This alerted the nearest redoubt garrison of 50 rifles and a Lewis gun which swept the Ottoman ranks.