d emperor when he found that
the Parthians were close at hand, that the frontier was crossed, and
that unless a treaty could be concluded he must risk a battle.

Under these circumstances the unwarlike emperor hurriedly, sent
ambassadors to the Parthian camp, with an offer to restore all the
prisoners made in the late campaign as the price of peace. Artabanus
unhesitatingly rejected the overture, but at the same time informed his
adversary of the terms on which he was willing to treat. Macrinus, he
said, must not only restore the prisoners, but must also consent to
rebuild all the towns and castles which Caracallus had laid in ruins,
must make compensation for the injury done to the tombs of the kings,
and further must cede Mesopotamia to the Parthians. It was impossible
for a Roman Emperor to consent to such demands without first trying the
fortune of war, and Macrinus accordingly made up his mind to fight a
battle. The Parthian prince had by this time advanced as far as Nisibis,
and it was in the neighborhood of that city that the great struggle took
place.

The battle of Nisibis, which terminated the long contest between Rome
and Parthia, was the fiercest and best-contested which was ever fought
between the rival powers. It lasted for the space of three days. The
army of Artabanus was numerous and well-appointed: like almost every
Parthian force, it was strong in cavalry and archers; and it had
moreover a novel addition of considerable importance, consisting of
a corps of picked soldiers, clad in complete armor, and carrying long
spears or lances, who were mounted on camels. The Roman legionaries
were supported by numerous light-armed troops, and a powerful body of
Mauritanian cavalry. According to Dio, the first engagement was brought
on accidentally by a contest which arose among the soldiers for the
possession of a watering-place. Herodian tells us that it commenced with
a fierce assault of the Parthian cavalry, who charged the Romans with
loud shouts, and poured into their ranks flight after flight of arrows.
A long struggle followed. The Romans suffered greatly from the bows of
the horse-archers, and from the lances of the corps mounted on camels;
and though, when they could reach their enemy, they had always the
superiority in close combat, yet after a while their losses from the
cavalry and camels forced them to retreat. As they retired they strewed
the ground with spiked balls and other contrivances for inju