In 980 C.E. Ryõgen (912-985) the head abbot of Enryaku temple on Mount Hiei in Kyõto, the Ennin faction of Tendai Buddhism, held a ceremony honouring Saichõ the founder of the Tendai sect of Buddhism. During the ceremony he insulted the high ranking monks from the Enchin faction of the Tendai sect by offering the highest seats to members of his own lineage.
This stirred the monks of the Enchin faction and from that day they harboured ill feelings towards the monks of the Ennin faction.
The following year, the imperial court appointed Yokei the abbot of Onjõ temple (Enchin faction) to be abbot of Hosshõ temple in Kyõto. Hosshõ temple was an important Tendai temple attached to the imperial regents of the Fujiwara clan. It was a tradition that head abbots of the Tendai sect be chosen from Hosshõ temple.
Ryõgen and the Ennin faction of Tendai immediately petitioned the imperial court. The imperial court didn’t budge in it’s decision and so Ryõgen and 160 militant monks marched down from Mount Hiei to the Fujiwara chieftains mansion in protest.
Under such pressure, under siege by the warrior monks of Mount Hiei, the court gave in and revoked their decision to appoint Yokei as abbot.
By this time rivalry between the two factions of Tendai Buddhism was palpable.
Following this Ryõgen was determined to prevent the Enchin faction from posing any similar threat to power in the future. He had lay members spread word throughout Kyõto that his monks would attack and destroy temples and buildings belonging to the Enchin faction.
This caused Yokei and his followers to take refuge in Onjõ temple. Yokei commanded three hundred monks to station themselves around the Mountain to guard the buildings and precious Buddhist treasures of the Enchin lineage. Armed monks were placed at strategic positions around Kyõto and at temples of the Enchin faction.
Yokei requested that the court intervene and so the imperial court issued an edict in 982 stating that members of the Enchin line should station armed guards at their buildings to protect them from possible attacks.
An attack didn’t take place however, and the edict was eventually lifted.
The imperial court hadn’t learned it’s lesson though and just seven years later in 989 (Ryõgen died in 985), Yokei was officially appointed head abbot of Tendai Buddhism by the imperial court.
Naturally, monks of the Ennin faction reacted immediately, coming down from Mount Hiei to stop the imperial messenger from delivering the edict and the messenger was chased back to the capital. Another messenger was sent but this time under imperial guard escort to ensure that the appointment was officially recieved.
Fearing for his life from the Ennin faction Tendai monks, Yokei employed “skillful warriors” for protection when he was to perform a ceremony on Mount Hiei. The Ennin monks tried to disrupt the Buddhist ceremony by firing arrows from the surrounding trees. The interruptions continued for the following months and many ceremonies were conducted with Yokei surrounded by armed monks holding the attackers at bay with their long halberds.
After just three months Yokei was forced to resign.
Four years later, monks of the Enchin faction burned an Ennin temple containing precious Buddhist sutras and statues to the ground. This resulted in a furious retaliation from the Ennin faction who burned down forty temples on Mount Hiei of the Enchin faction.
The monks of the Enchin line subsequently left the mountain altogether - this was the beginning of the physical separation of the two factions of Tendai Buddhism which came to be known as the Mountain Gate Lineage and the Temple Gate Lineage.