Complex sentence: Dax leads the first wave of soldiers over the top into no man's land under heavy fire, but not one of the men reach the German trenches, and B Company refuse to leave their own trench after sustaining heavy casualties.
Split into simpler sentences: Dax leads the first wave of soldiers over the top into no man's land under heavy fire, but the attack is a failure. None of the men reach the German trenches, and B Company refuse to leave their own trench after sustaining heavy casualties.