He afterwards commanded an army of ninety-five thousand Arabs and
Persians, sent by his father to invade the Eastern Roman Empire,
which was then ruled by the Empress Irene (i-re'-ne). After defeating
Irene's famous general, Nicetas (ni-ce'-tas), Harun marched his
army to Chrysopolis (Chrys-op'-o-lis), now Scutari (skoo'-ta-re),
on the Asiatic coast, opposite Constantinople. He encamped on the
heights, in full view of the Roman capital.

The Empress saw that the city would certainly by taken by the Moslems.
She therefore sent ambassadors to Harun to arrange terms; but he
sternly refused to agree to anything except immediate surrender.

Then one of the ambassadors said, "The Empress has heard much of
your ability as a general. Though you are her enemy, she admires
you as a soldier."

These flattering words were pleasing to Harun. He walked to and
fro in front of his tent and then spoke again to the ambassadors.

"Tell the Empress," he said, "that I will spare Constantinople if
she will pay me seventy thousand pieces of gold as a yearly tribute.
If the tribute is regularly paid Constantinople shall not be harmed
by any Moslem force."

The Empress had to agree to these terms. She paid the first year's
tribute; and soon the great Moslem army set out on its homeward
march.

When Harun was not quite twenty-one years old he became caliph.