Complex sentence: But by the 2nd century BC conflicts and wars arose between the Salyens and the Greeks of Marseille, who not having a powerful army, called upon the assistance of their Roman allies.
Split into simpler sentences: But by the 2nd century there conflicts and wars between the Salyens and the Greeks of Marseille. The Greeks of Marseille, not having a powerful army, called upon the assistance of their Roman allies.