In contrast, Roman expansion into Spain and Gaul occurred as a mix of alliance-seeking and military occupation. In the 2nd century BC, Roman involvement in the Greek east remained a matter of alliance-seeking, but this time in the face of major powers that could rival Rome. According to Polybius, who sought to trace how Rome came to dominate the Greek east in less than a century, this was mainly a matter of several Greek city-states seeking Roman protection against the Macedonian kingdom and Seleucid Empire in the face of destabilisation created by the weakening of Ptolemaic Egypt. In contrast to the west, the Greek east had been dominated by major empires for centuries, and Roman influence and alliance-seeking led to wars with these empires that further weakened them and therefore created an unstable power vacuum that only Rome could fill. This had some important similarities to (and important differences from) the events in Italy centuries earlier, but this time on a global scale.