Until the 21st century, the two main factions of Heiren, the Heir'och and the Heir'tza, resided on the planet in relative peace. However at the time, the Heir'och abandoned their homeworld and settled on a neighboring planet, which they named Heir'ocha. As the Heir'tza now had their homeworld to themselves, tensions between the two factions remained rather low.
However after a century, an interplanetary war broke out between the two planets which was started over ecomomic, cultural, and religious reasons. The war raged for nearly a century, but eventually a cease fire was drawn up. Despite the tentative peace, the governments on both planets kept their military spending up and the two were ready for the war to begin at a moment's notice.
In the late 22nd century, it was discovered that once or twice in a generation, a powerful telepath is born. Both sides realised that the best chance for reconciliation was for a telepath to be born to each side. This didn't occur until the mid-23rd century, and then preparations began for the reconciliation.
In 2251, the ceremony of reconciliation was planned to take place in the capital city of Heir'at. Even though modern technology and weapons weren't allowed at the ceremony, there were still concerns that members of each faction would attempt to assassinate the telepaths. (TOS - My Brother's Keeper novel: Republic)