and reached the important strategic town of Pelusium in November 170 BC. Just as the Ptolemaic army moved out of Pelusium to begin its invasion of Coele-Syria, the Seleucids defeated the Ptolemaic army in the Sinai desert, perhaps due to Egyptian surprise at the Seleucids being ready to fight immediately. Ptolemaic losses mounted as they retreated to Pelusium, but Pelusium quickly fell with little loss of life and a surrender of the Ptolemaic army. Pelusium was the gateway to the rest of Egypt; with it under control, Seleucid supply lines were secure, and Egypt was in grave danger. Antiochus took Naucratis and camped near Alexandria, potentially threatening a siege. The Egyptians suffered internal unrest over the poor progress of the war: Eulaeus and Lenaeus were overthrown and replaced by two new regents, Comanus and Cineas. Envoys were sent to negotiate a peace treaty. Antiochus took Ptolemy VI (who was his nephew) under his guardianship, perhaps with the intent of making Egypt a client state subordinate to Seleucid power. Archaeological records show that even Thebes in the southern part of Egypt were occupied by a foreign army (surely the Seleucids) in October 169 BC. However, this occupation was unacceptable to the people of Alexandria who responded by proclaiming Ptolemy Physcon as sole king. Antiochus besieged Alexandria but he was unable to cut communications to the city so, in late autumn of 169, he withdrew his army, leaving Ptolemy VI as a rival king in Memphis. Antiochus possibly withdrew to deal with problems in Phoenicia at home. In Antiochus's absence, Ptolemy VI and his brother Ptolemy Physcon were reconciled, possibly after a brief civil struggle. Antiochus, angered at his loss of control over the king, invaded again in 168 BC. The Egyptians sent to Rome asking for help and the Senate dispatched Gaius Popilius Laenas to Alexandria. Meanwhile, a Seleucid fleet seized Cyprus, and Antiochus's army took Memphis again. While at Memphis, he even issued an official decree as Egyptian king. The Ptolemaic armies failed to offer any major field battles, instead staying fortified in garrisons. Antiochus was now prepared to march on the capital of Alexandria again. At Eleusis, on the outskirts of Alexandria, he met Popilius Laenas, with whom he had been friends during his stay in Rome. But instead of a friendly welcome, Popilius offered the king an ultimatum from the Roman Senate: he must evacuate Egypt and Cyprus