He was a high priest like his father and uncle, Jonathan, before him. The initial stages of his leadership were a time of trepidation. Antiochus VII (Sidetes), the last powerful ruler of the Seleucid dynasty in Syria, after seeking John’s assistance in obtaining the Seleucid throne, turned upon him and for a short while it appeared as though Jewish independence was in jeopardy. Antiochus even laid siege to Jerusalem, but was eventually repelled. Hasmonean forces even joined the pagan ruler on a campaign (during which, at one point, the entire Seleucid army was held up for several days as the Jewish contingent celebrated the holiday of Pentecost).
Hyrcanus took immediate advantage of Antiochus’s disappearance from the scene in 129 and commenced his consolidation and further expansion southward, northward, and eastward. Idumea (home of the biblical Edomites) came under Jewish dominion, with the Edomite population accepting conversion, and placing themselves thenceforth squarely in the Jewish camp.
To the north, the capital of the hostile Samaritans, Shechem, and eventually also the town of Samaria, were demolished by John's armies. In addition to this expansion into Lower Galilee, areas across the Jordan also fell into Jewish hands.
One unfortunate development marred Hyrcanus’ years — the Pharisee-Sadducee schism. The Talmud and other ancient rabbinical sources display an ambivalent attitude toward John. Despite the accusation that he turned Sadducee toward the end, the Talmud credits him with important religious decisions. He may have been the first of the Hasmonean dynasty to strike coins of his own, a sign of independence in the ancient world.
John renewed the friendship treaty with Rome initiated by Judah Maccabee. He elicited several additional important declarations of support from Rome for the territorial integrity of the Hasmonean domain, and a declaration of friendship from Pergamum in Asia Minor.
Quotes from others about the person
His reign, says Josephus, the ancient Jewish historian, was a happy one, an indubitable indication of economic well-being. Certainly in the demographic-territorial domain he vastly outshone his forebears.