Complex sentence: In 72 B.C. the Roman General Pompey, while on the way back to Rome and after a military campaign in Spain founded a Roman colony there to defend the passage to the Val d'Aran and the Iberian peninsula.
Split into simpler sentences: In 72 B.C. the Roman General Pompey, while on the way back to Rome after a military campaign in Spain founded a Roman colony there. The goal was to defend the passage to the Val d'Aran and the Iberian peninsula.