Then, as soon as the Republic had secured its hold on Roman affairs and the Lombard trade, we saw its irresistible need of access to the sea, and that a war of extermination with Pisa had become altogether inevitable. To suppose that this prolonged, constantly renewed and sanguinary conflict was solely caused by a blind instinctive hatred of Pisa, when other and more serious reasons were so plainly existent, would be to deny the evidence of facts. From beginning to end it was simply the clash of violently opposed interests. The Pisans were perfectly aware that to yield a free passage to the power already commanding the chief trade in the interior of Italy--the power that, without having as yet a single galley afloat, had already made its way to all the harbours of the East--the power so persistently struggling for absolute supremacy in Tuscany--could only lead to their own lasting subjection. Therefore they resisted to the utmost of their strength. Their resources were undoubtedly great, and as many other Italians were equally hostile to the supremacy of Florence, the latter could never have succeeded in reducing the Pisans, had it not constantly employed the shrewdest devices in addition to its efforts in the field. In fact there is no better proof of the political ability of the Florentines than their mode of conducting this war and the means they employed to attain the object that, throughout the whole course of their history, had been their chief and invariable aim. We find them steadfast in their friendship to Lucca, and always prompt to succour that city at all costs, because Lucca was never well disposed to the Pisans, and might prove a most useful ally in any campaign against them. So, too, we always find Florence on good terms with Genoa, and avoiding every risk of giving offence to a power that was Pisa's natural rival on the seas. Indeed, the Florentines always did their best to foster that rivalry, inasmuch as without an ally strong enough to assist them by crushing Pisa's power by sea, they could never hope to overthrow it by land. And at last the Pisans were defeated by the Genoese in the naval battle of Meloria (August 6, 1284). From that day the conquest of Pisa by the Florentines, although still to be long contested, was a foregone conclusion, and from that moment also their friendship for the Genoese began to lose warmth. While desiring assistance in overcoming Pisa, they wished to avoid aggrandising the power of a Ghibelline republic, already very mighty on the sea. Accordingly, after having so furiously attacked and enfeebled Pisa, we find them aiding that state to withstand the Genoese, until the moment came when the latter having abandoned the idea of conquering Pisa, they could successfully undertake its conquest on their own account.