The Rhodians endeavoured to make up for the time they had lost, and the money they had expended, during their war with Antiochus, by applying themselves entirely to navigation and commerce; so that, according to Polybius, they became masters of the sea, and the most opulent and flourishing state of those times. The next war in which they were engaged was occasioned entirely by their attention and regard to their commercial interests. We have already slightly noticed this war; but in this place it will be proper to go more into detail respecting it. The people of Byzantium determined to lay a toll on all ships that traded to the Euxine, in order to defray an annual tribute which they were obliged to pay to the Greeks. As one of the most important and lucrative branches of the commerce of Rhodes was to the countries lying on this sea, they were much aggrieved by this toll, and endeavoured to persuade the Byzantines to take it off, but in vain. Under these circumstances, they, in conjunction with Prusias, king of Bythinia, declared war against the Byzantines; and while their ally took Hieron, which seems to have been a great mart of the Byzantines, and the resort of most of the merchants trading to these parts, the Rhodians, with a powerful fleet, ravaged their coasts, and seized all their ships trading to the Euxine. The war was at length terminated under the mediation of the king of the Thracian Gauls; the Byzantines agreeing to take off the toll.
Their success in this war was counterbalanced by a dreadful earthquake, which threw down the Colossus, destroyed the arsenal, and damaged part of the walls and city. As the Rhodians, however, were much esteemed by most of their neighbours, who found their prosperity intimately connected with the prosperity of Rhodes, they soon recovered from these calamities and losses. Hiero, king of Syracuse, gave them 100 talents, and exempted them from all duties and taxes. Ptolemy gave them also the like sum, besides one million measures of wheat, and timber, etc. requisite for building fifty ships. Antiochus exempted all their vessels, which traded to his ports, from every kind of tax and duty. They received from other princes presents or privileges of equal importance and value; so that, in a very short time, they recovered their former opulence and trade, and rebuilt their walls, etc.
Their alliance with Attalus, king of Pergamus, involved them in a war with Philip king of Macedonia, and was the cause of their forming an alliance with the Romans. In this war the Rhodian fleet, in conjunction with the fleets of their allies, gained several victories over the fleet of Philip. The latter was at length obliged to sue to the Romans for peace, and they, in fixing the terms, included the Rhodians, to whom were ceded Stratonice, and the greater part of Caria. In the meantime Antiochus and the Romans had commenced hostilities, and the Rhodians were again involved in them: almost at their very commencement, their fleet was surprized by a stratagem of Antiochus's admiral, and of thirty ships of war of which it consisted, only seven escaped.
They soon, however, repaired their losses, and fitted out another fleet, with which they put to sea, for the purpose of preventing the junction of Hannibal with Antiochus's ships: the former had thirty-seven large ships; the Rhodian fleet was nearly equal in numbers, but inferior in size. The hostile fleets met off the coast of Pamphilia. The battle was obstinate: at first, by an oversight of the Rhodian admiral, some disorder occurred in part of his fleet; but this was soon repaired, and a decisive victory obtained. Part of Hannibal's fleet was captured, and the rest blocked up in the harbours of Pamphilia. The defeat of Antiochus, both at sea and land, by the Romans, to which we have already adverted, obliged this monarch to sue for peace, in which the Rhodians were included.
We have now arrived at that period of the history of Rhodes when the first difference arose between that city and the Romans: the latter suspected that the Rhodians favoured Perseus king of Macedon, with whom they were at war, and were moreover displeased at their presuming to interfere with them in his favour. In order to watch their inclinations and motions, the senate sent three commissioners to Rhodes: these found a fleet of forty galleys, which there was reason to believe had been intended to act against the Romans; but which, by the advice of the chief magistrate, were, on the arrival of the commissioners, ordered to sea, to act in union with them. Scarce, however, were the commissioners departed, when the Rhodians became lukewarm in the cause of the Romans; and although they sent a few of their galleys to join the Roman admiral, they kept the greatest number in port, waiting the issue of the war between them and the king of Macedonia. As soon as they heard of the defeat of the former in Thessaly, they entered into negotiations with Perseus, and at the same time sent ambassadors to Rome, who complained, that in consequence of the war between Perseus and the Romans, the navigation and commerce of Rhodes was greatly injured, their island deprived of provisions and other necessaries, and the customs and duties which their maritime situation formerly afforded them kept back, from their no longer being able to sail with safety along the coasts of Asia, where they used to levy the most important and productive of them.
After the defeat of Perseus, they ceased to remonstrate, and became submissive to the Romans. It is probable, however, that the Romans would have seized this opportunity of attacking them, had not Cato spoken very strongly in their favour: in consequence of his arguments and influence, and by the cession of Lycia and Caria, they were again admitted to an alliance with the Romans.
The advantages they derived from this alliance were so great, that they resisted the promises and the threats of Mithridates, when he engaged in hostilities with the Romans. This monarch, therefore, resolved to employ his whole force by sea and land against them: they were not however dismayed, but placed a firm reliance on their skill in maritime affairs. They divided their fleet into three squadrons: one drawn up in a line protected the entrance of the harbour; and the other two, at a greater distance from the shore, were stationed to watch the approach of the enemy. Mithridates also divided his fleet, which was more numerous than that of the Rhodians, into three squadrons; one of these he himself commanded, on board of a quinquereme, and directed to attack the squadron which was protecting the port. The Rhodians gradually retired before the enemy, till they came close to the mouth of the harbour: Mithridates in vain endeavoured to break their line, and force an entrance; in all his attempts he was defeated with considerable loss; and his land forces, which he had embarked in transports, being dispersed in a storm, he was obliged to retire from before the city.
The Romans acknowledged the benefits they derived from the valour of the Rhodians on this occasion; and they again experienced it, in the war which Pompey carried on against the Cilician pirates, though that commander took all the merit to himself. In the civil war between him and Caesar, they assisted the former with a numerous fleet, under the command of one of their best seamen, who distinguished himself above all Pompey's captains, and gained very considerable advantages over Caesar's fleet. On the death of Pompey they joined Csesar: this exposed them to the hostility of Cassius; they endeavoured to pacify him by promising to recal the ships they had sent to the assistance of Caesar, but he demanded the delivery of their whole fleet, and that he should be put in possession of their harbour and city. To these terms they would not accede, but prepared for war, by equipping a fleet of thirty-three ships, and placing it under the command of one of their best officers. A battle ensued which was fought on both sides with great skill and bravery; but the Rhodians were obliged to yield to the superior number of the Roman fleet, and to return to the harbour, having lost two of their ships, and the rest being very much damaged. It is remarked by the ancient historians who relate this battle, that it was the first time the Rhodians were fairly overcome in a sea-fight.
Cassius followed up his success by bringing against Rhodes a fleet of eighty ships of war, and 200 transports. Against this formidable armament the Rhodians again put to sea, and a second battle ensued, which was more obstinately contested than the first: the Romans however were again victorious, and the city of Rhodes was blocked up by sea and land. Its fate was soon determined; for some of the inhabitants, dreading a famine, opened the gates to the Romans. Cassius, besides other severe terms, obliged the Rhodians to deliver up all their ships, and all their public treasures; the temples were plundered, and 8000 talents extorted from private individuals, besides a fine of 500 levied on the city.
From this time till the reign of Vespasian, when the island became a Roman province, it was sometimes oppressed, and sometimes favoured by the Romans; according, as Tacitus remarks, as they obliged them with their assistance in foreign wars, or provoked them with their seditions at home.