Philip wished to cut off the resources and stepping-stones of the Romans in those parts.
So that if he meant to cross again to Asia, he might have <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a> as a stepping-stone.
To describe at length the position of <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a> and Sestus and the peculiar advantages of those cities seems to me useless, as every one who has the least claim to intelligence has acquired some knowledge of them owing to the singularity of their position,
but I think it of some use for my present purpose to recall it summarily to the minds of my readers so as to fix their attention on it.
One can form an idea of the facts about these cities not so much from a study of their actual topography as from dwelling on the comparison I am about to adduce.
For just as it is impossible to sail from the sea called by some the Ocean and by others the Atlantic Sea into our own sea except by passing through the mouth of it at the Pillars of Heracles,
so no one can reach the Euxine and Propontis from our sea except by sailing through the passage between Sestus and <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a>.
Now, just as if chance in forming these two straits had exercised a certain proportion, the passage at the Pillars of Heracles is far wider than the <a class="linkToPlace" target="_blank" href="/place?placename=Hellespont&groupId=620&placeId=1141">Hellespont</a>,
being sixty stades in width while the width of the latter at <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a> is two stades, just as if this distance had been designed owing to the Ocean being many times the size of this sea of ours.
The natural advantages, however, of the entrance at <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a> far excel those of that at the Pillars of Heracles.
For the former, lying as it does between two inhabited districts, somewhat resembles a gate owing to the free intercourse it affords, being sometimes bridged over by those who intend to pass on foot from one continent to the other and at other times constantly traversed by boats,
while the latter is used by few and rarely for passage either from sea to sea or from land to land, owing to the lack of intercourse between the peoples inhabiting the extremities of <a class="linkToPlace" target="_blank" href="/place?placename=Africa&groupId=300&placeId=294">Africa</a> and Europe and owing to our ignorance of the outer sea.
The city of <a class="linkToPlace" target="_blank" href="/place?placename=Abydus&groupId=268&placeId=523">Abydus</a> itself lies between two capes on the European shore and has a harbour which affords protection from all winds.
Without putting in to the harbour it is absolutely impossible to anchor off the city owing to the swiftness and strength of the current in the straits.
Walbank Commentary