The First Macedonian War strengthened the hand of Philip V. While Rome was dealing with Carthage, Philip was trying to increase his influence in Greece and its environs. His eyes fell on the Egyptian subcontinent in the Aegean Sea. After the death of Ptolemy IV in 203/204 BC, his four-year-old son Philip ascended the throne as the fifth Ptolemy.He allied himself with the Syrian emperor Antiochus III. The treaty was that the shores of the Aegean Sea would be occupied by Philip, and Antiochus would be taken over by Phenicia and Palestine. Ptolemy's advisers, inspired by the plans of Philip and Antiochus, sent a message of help to Rome as a friend.
Meanwhile, as part of a conspiracy with Antiochus, Philip began to increase his naval power. Its purpose was to extend its power to the former Hellespont (now the Dardanelles, connecting Europe and Asia). For that purpose he laid siege to the island of Chaos to establish a base in the Central Aegean Sea.
Chaos and Ladder Naval War (201 BC): King Atlas of Pergamon and the Rhodian navy set out to intercept Philip. Philip had about 200 ships, small and large, while his opponent's ships were only about 75.
Atlas and Rodian grabbed him from behind. When Philip's flag-carrying ship hit an enemy ship and got stuck, Pergamon's ship destroyed it, leaving many warriors, including Philip's Admiral, buried. The Rhodes attacked another part of the Macedonian fleet. Their sailors had more skills and experience than the Macedonians, so they were able to defeat Philip's forces.
Philip fled and fell, defeating Atlas and Rodian in a land battle and advancing on Rhodes. Here another naval battle took place near Ladder. However, there are differences of opinion as to who won the war. However, Philip's desire to establish dominance in the sea was not fulfilled. In the winter of 201-200 BC, he was again surrounded by Atlas and Rhodians in the Gulf of Berglia. Philip somehow managed to escape. He then abandoned his plan to establish Macedonia as a naval power.
Occupation of Abydos and the Ultimatum of Rome: In the spring of 200 BC, Philip's forces laid siege to Abydos, wreaking havoc on the coast of Thrace. This city needs him to control Hellespont. After a fierce battle, his army broke down the city's defensive wall. All male citizens of the city are killed, women and children are taken prisoner.Around the same time, Marcus Amelius Lepidus, as ambassador to the Roman Senate, brought a message to Philip at the request of Egypt, Atlas, and the Rhodes. He was conditional on the immediate cessation of all military aggression in Greece, the recognition of Ptolemy V's authority in Egypt and its territories, and the acceptance of mediation by the Roman Senate to resolve disputes with the Atlas and the Rhodes.The Senate knew full well that Philip would not obey. So when he naturally ignored Rome's conditions, Rome called for war against Macedonia.