Koinonian Wars

From Memory Alpha, the free Star Trek reference

The Koinonian Wars were a series of conflicts fought by different factions of the corporeal Koinonians many centuries before the 24th century.

The Koinonians became embroiled in a war that lasted for several generations and, according to historical records, finally destroyed the entire race. The non-corporeal Koinonians were watching as their corporeal neighbors destroyed their race in endless and bitter wars, but did not interfere.

Buried subspace proximity detonators hidden in underground caverns and tunnels on the Koinonian homeworld were all that remained of the war. (TNG: "The Bonding")