Complex sentence: They were in action for the first time in what was known as the Battle of Sari Bair Ridge, held up by concealed trenches, lack of water, heat and exhaustion, losing over 80 killed by dusk when they withdrew.
Split into simpler sentences: They were in action for the first time in what was known as the Battle of Sari Bair Ridge. Held up by concealed trenches, lack of water, heat and exhaustion, they lost over 80 killed by dusk when they withdrew.