Expecting an easy victory, the Persians besieged the town of Phasis in Lazica, held by the Byzantines, but were defeated in the ensuing irregular battle.

In the spring of 555, the Persian general Nachoragan took the initiative in besieging the major Laz-Byzantine stronghold, the town of Phasis, which lay at the mouth of the namesake river.

The Byzantine forces of the area were led by the magister militum per Armeniam Martin and his second-in-command Justin, son of Germanus.

Nachoragan's forces however emptied the moat after days of hard work, and managed to surround the town from its river side too by building a bridge of boats across the Phasis.

[8] Angilas is recorded leading a regiment of Moorish peltasts and spearmen, probably meaning they were only armed with shield and lances.

The encircled Byzantines however began a desperate attack on the enemies positioned closer to the town walls, and the Dailamites "opened up their ranks and made way from them" instead of standing their ground.

[2][9] Martin eventually conceived a ruse of war, which would both raise the morale of his soldiers and spread fear in enemy units.

The fabricated message congratulated the defenders for their valour and informed them that reinforcements were approaching, and the "messenger" claimed that they were camped near the River Neocnus, at a short distance from the town itself.

Martin then feigned indignation that newcomers would share the glory and spoil "with those who had borne the burden and the heat", to which his troops shouted their approval, being motivated to action.

[8] While Nachoragan was forming his plan, Justin decided to take advantage of the calm before the storm: he exited the city, leading a force of 5,000 men cavalrymen and an infantry brigade to "a church of great sanctity in the vicinity".

Arrows and darts filled the air, while Sassanid siege weapons were attempting to destroy the wooden walls.

[5][8] Panicked Sassanid troops started to retreat, and most of the Dailamites left their positions to "relieve those who were being hard pressed".

The other Dailamites noted that their kinsmen were in peril and abandoned their current positions in an attempt to face Angilas and Theodore, but their counterattack was disorganized and ineffective.

[2][11] The nearby Persian forces in turn thought that the Dailamites were retreating in haste, panicked and started fleeing "ignominiously in all directions".

[8][11] By the time night fell, the Persians had reportedly lost at least ten thousand fighting men (mostly the paygan forces)[12] and most of their siege equipment.

The servants and porters of the Sassanid army reportedly mistook the smoke for a sign that the city had fallen, and started rushing towards the Byzantine lines.

"His skin, torn off in one piece from head to foot, so as to retain the shape of the body, was sewn up and inflated like a bladder".