e Persian dominions did not as yet
touch. Once in possesion of this tract, Chosroes conceived that he might
launch a fleet upon the Euxine, command its commerce, threaten or ravage
its shores, and even sail against Constantinople and besiege the Roman
emperor in his capital. The Persian king therefore acceded to the
request of the envoys, and, pretending to be called into Iberia by a
threatened invasion of the Huns, led a large army to the Lazic border,
was conducted into the heart of the country by the envoys, received the
submission of Gubazes, the king, and then, pressing on to the coast,
formed the siege of Petra, where the Roman forces were collected. Petra
offered a stout resistance, and repulsed more than one Persian assault;
but it was impossible for the small garrison to cope with the numbers,
the engineering skill, and the ardor of the assailants. After the loss
of their commandant, Johannes, and the fall of one of the principal
towers, the soldiers capitulated; Petra was made over to the Persians,
who restored and strengthened its defences, and Lazica became for the
time a Persian province.

II. The War in Mesopotamia.--Belisarius, on reaching the eastern
frontier, fixed his head-quarters at Daras, and, finding that the
Persians had no intention of invading Syria or Roman Mesopotamia,
resolved to lead his troops into the enemy's territory. As his forces
were weak in numbers, ill-armed, and ill-supplied, he could scarcely
hope to accomplish any great enterprise; but it was important to recover
the Roman prestige after the occurrences of the preceding year, and to
show that Rome was willing to encounter in the open field any force that
the Persians could bring against her. He therefore crossed the frontier
and advanced in the direction of Nisibis, less with the intention of
attacking the town than of distinctly offering battle to the troops
collected within it. His scheme succeeded; a small force, which he threw
out in advance, drew the enemy from the walls; and their pursuit of
this detachment brought them into contact with the main army of
Belisarius, which repulsed them and sent them flying into the town.
Having thus established his superiority in the field, the Roman general,
though he could not attack Nisibis with any prospect of success, was
able to adopt other offensive measures. He advanced in person a day's
march beyond Nisibis, and captured the fort of Sisauranon. Eight hundred
Persian cavalry of th