The Ushaan was a crucial part of Andorian tradition, a code of honor demanding a duel to the death in which the combatants fought against each other with an ice miner's tool, the ushaan-tor, while tethered to each other. An enormous body of rules and regulations existed around this code of honor, summing up to 12,000 amendments.
The Ushaan could be demanded by someone as a means of personal vengeance, for example to avenge a personal loss. However, there existed a right of substitution, allowing each combatant to put up a replacement for themselves. Furthermore a married combatant could postpone a duel indefinitely, if there were no children to continue their clan. Additionally, the fight may be called off, if one combatant disabled the other in such a way that they could not continue the duel.
Commander Shran challenged the Tellarite Naarg to Ushaan in 2154 after Naarg caused the death of Shran's lover Talas. To prevent a diplomatic incident, Jonathan Archer fought in Naarg's place. The Ushaan was settled when Archer incapacitated Shran by severing his left antenna. (ENT: "United")