Complex sentence: The guerrillas retreated into well-camouflaged foxholes as the Rhodesians moved forward, the RLI now joined by most of the Selous Scouts, who left their vehicles outside the town.
Split into simpler sentences: The guerrillas retreated into well-camouflaged foxholes as the Rhodesians moved forward. The RLI men were now joined by most of the Selous Scouts, who left their vehicles outside the town.