Both sides exerted themselves to push forward their trenches as far as possible, and the earthworks advanced but slowly amidst constant conflicts. At the same time skirmishing went on on the opposite side of Caesar's camp with the garrison of Dyrrhachium; Caesar hoped to get the fortress into his power by means of an understanding with some of its inmates, but was prevented by the enemy's fleet. There was incessant fighting at very different points - on one of the hottest days at six places simultaneously - and, as a rule, the tried valour of the Caesarians had the advantage in these skirmishes; once, for instance, a single cohort maintained itself in its entrenchments against four legions for several hours, till support came up. No prominent success was attained on either side; yet the effects of the investment came by degrees to be oppressively felt by the Pompeians. The stopping of the rivulets flowing from the heights into the plain compelled them to be content with scanty and bad well-water. Still more severely felt was the want of fodder for the beasts of burden and the horses, which the fleet was unable adequately to remedy; numbers of them died, and it was of but little avail that the horses were conveyed by the fleet to Dyrrhachium, because there also they did not find sufficient fodder.
Pompeius could not much longer delay to free himself from his disagreeable position by a blow struck against the enemy. He was informed by Celtic deserters that the enemy had neglected to secure the beach between his two chains of entrenchments 600 feet distant from each other by a cross-wall, and on this he formed his plan. While he caused the inner line of Caesar's entrenchments to be attacked by the legions from the camp, and the outer line by the light troops placed in vessels and landed beyond the enemy's entrenchments, a third division landed in the space left between the two lines and attacked in the rear their already sufficiently occupied defenders.
The entrenchment next to the sea was taken, and the garrison fled in wild confusion; with difficulty the commander of the next trench Marcus Antonius succeeded in maintaining it and in setting a limit for the moment to the advance of the Pompeians; but; apart from the considerable loss, the outermost entrenchment along the sea remained in the hands of the Pompeians and the lin was broken through. Caesar the more eagerly seized the opportunity, which soon after presented itself, of attacking a Pompeian legion, which had incautiously become isolated, with the bulk of his infantry. But the attacked offered valiant resistance, and, as the ground on which the fight took place had been several times employed for the encampment of larger and lesser divisions and was intersected in various directions by mounds and ditches, Caesar's right wing along with the cavalry entirely missed its way; instead of supporting the left in attacking the Pompeian legion, it got into a narrow trench that led from one of the old camps towards the river. So Pompeius, who came up in all haste with five legions to the aid of his troops, found the two wings of the enemy separated from each other, and one of them in an utterly forlorn position. When the Caesarians saw him advance, a panic seized them; the whole plunged into disorderly flight; and, if the matter ended with the loss of 1000 of the best soldiers and Caesar's army did not sustain a complete defeat, this was due simply to the circumstance that Pompeius also could not freely develop his force on the broken ground, and to the further fact that, fearing a stratagem, he at first held back his troops.
But, even as it was, these days were fraught with mischief. Not only had Caesar endured the most serious losses and forfeited at a blow his entrenchments, the result of four months of gigantic labour; he was by the recent engagements thrown back again exactly to the point from which he had set out. From the sea he was more completely driven than ever, since Pompeius' elder son Gnaeus had by a bold attack partly burnt, partly carried off, Caesar's few ships of war lying in the port of Oricum, and had soon afterwards also set fire to the transport fleet that was left behind in Lissus; all possibility of bringing up fresh reinforcements to Caesar by sea from Brundisium was thus lost. The numerous Pompeian cavalry, now released from their confinement, poured themselves over the adjacent country and threatened to render the provisioning of Caesar's army, which had always been difficult, utterly impossible.
Caesar's daring enterprise of carrying on offensive operations without ships against an enemy in command of the sea and resting on his fleet had totally failed. On what had hitherto been the theatre of war he found himself in presence of an impregnable defensive position, and unable to strike a serious blow either against Dyrrhachium or against the hostile army; on the other hand it depended now solely on Pompeius whether he should proceed to attack under the most favourable circumstances an antagonist already in grave danger as to his means of subsistence. The war had arrived at a crisis. Hitherto Pompeius had, to all appearance, played the game of war without special plan, and only adjusted his defence according to the exigencies of each attack; and this was not to be censured, for the protraction of the war gave him opportunity of making his recruits capable of fighting, of bringing up his reserves, and of bringing more fully into play the superiority of his fleet in the Adriatic. Caesar was beaten not merely in tactics but also in strategy. This defeat had not, it is true, that effect which Pompeius not without reason expected; the eminent soldierly energy of Caesar's veterans did not allow matters to come to an immediate and total breaking up of the army by hunger and mutiny. But yet it seemed as if it depended solely on his opponent by judiciously following up his victory to reap its full fruits.
It was for Pompeius to assume the aggressive; and he was resolved to do so. Three different ways of rendering his victory fruitful presented themselves to him. The first and simplest was not to desist from assailing the vanquished army, and, if it departed, to pursue it. Secondly, Pompeius might leave Caesar himself and his best troops in Greece, and might cross in person, as he had long been making preparations for doing, with the main army to Italy, where the feeling was decidedly antimonarchical and the forces of Caesar, after the despatch of the best troops and their brave and trustworthy commandant to the Greek army, would not be of very much moment. Lastly, the victor might turn inland, effect a junction with the legions of Metellus Scipio, and attempt to capture the troops of Caesar stationed in the interior.
The latter forsooth had, immediately after the arrival of the second freight from Italy, on the one hand despatched strong detachments to Aetolia and Thessaly to procure means of subsistence for his army, and on the other had ordered a corps of two legions under Gnaeus Domitius Calvinus to advance on the Egnatian highway towards Macedonia, with the view of intercepting and if possible defeating in detail the corps of Scipio advancing on the same road from Thessalonica. Calvinus and Scipio had already approached within a few miles of each other, when Scipio suddenly turned southward and, rapidly crossing the Haliacmon (Inje Karasu) and leaving his baggage there under Marcus Favonius, penetrated into Thessaly, in order to attack with superior force Caesar's legion of recruits employed in the reduction of the country under Lucius Cassius Longinus.
But Longinus retired over the mountains towards Ambracia to join the detachment under Gnaeus Calvisius Sabinus sent by Caesar to Aetolia, and Scipio could only cause him to be pursued by his Thracian cavalry, for Calvinus threatened his reserve left behind under Favonius on the Haliacmon with the same fate which he had himself destined for Longinus. So Calvinus and Scipio met again on the Haliacmon, and encamped there for a considerable time opposite to each other.
Pompeius might choose among these plans; no choice was left to Caesar. After that unfortunate engagement he entered on his retreat to Apollonia. Pompeius followed. The march from Dyrrhachium to Apollonia along a difficult road crossed by several rivers was no easy task for a defeated army pursued by the enemy; but the dexterous leadership of their general and the indestructible marching energy of the soldiers compelled Pompeius after four days' pursuit to suspend it as useless.
He had now to decide between the Italian expedition and the march into the interior. However advisable and attractive the former might seem, and though various voices were raised in its favour, he preferred not to abandon the corps of Scipio, the more especially as he hoped by this march to get the corps of Calvinus into his hands. Calvinus lay at the moment on the Egnatian road at Heraclea Lyncestis, between Pompeius and Scipio, and, after Caesar had retreated to Apollonia, farther distant from the latter than from the great army of Pompeius;
