The Battle of Sector 83 occurred between the Army of Light and the Shadows in late 2260 in Sector 83, one of the many engagements in the Second Shadow War. Despite suffering heavy casualties, the Alliance managed to score an important victory.
By the end of 2260, the Shadows had begun a major assault on the younger races. Most of the major powers were either crippled or had removed themselves from the conflict, leaving many of the other younger races to be decimated by the Shadow attacks for months on end. The Army of Light was formed at Babylon 5 to oppose the Shadows.
The one vital piece of information obtained by the Alliance was that the Shadow vessels were vulnerable to being "stunned" by telepathic interference, leaving them vulnerable to concentrated fire from the younger vessels. Volunteer telepaths (largely Minbari) were quickly put into place aboard Alliance ships to strike back against the enemy.
John Sheridan and Delenn assembled a fleet of the League of Non-Aligned Worlds and anyone else who would stand with them together to fight against the Shadows. They deduced that the Shadows were attempting to drive refugee ships into Sector 83, corralling them together, then hitting them once to devastate the younger races physically and demoralize them probably beyond recovery. Having realized this, Sheridan and Delenn assemble an attack fleet and send Susan Ivanova and Marcus Cole ahead in a White Star to scout the sector for signs of Shadow activity. The first wave of the White Star fleet (having been assembled in secret by the Minbari) is ready just in time to take part in the battle.
Shortly after engaging and destroying a lone Shadow scout vessel, the White Star discovers a massive Shadow armada jumping into space, preparing their strike. They send a signal to the rest of the fleet. The White Star itself suffered minor engine damage while engaging the scout, but is able to quickly repair them and take part in the battle.
Sheridan and Delenn used the Minbari cruiser Dogato as their flagship, coordinating the attack from the main holographic chamber. Many telepaths were brought along, most of whom were Minbari and operated from the Sharlin class warships.
The Army of Light jumps into normal space and engages the Shadows in a pitched battle.
The battle lists both ways. Both sides were about even in total numbers of ships. The Shadows were caught by surprise and the Alliance had telepaths on their side, but the ancient Shadows and their powerful vessels were not easily dispatched. They quickly assemble their smaller fighters to act as buffers between the telepaths and the heavier warships. They then attempt to outflank the Alliance fleet, succeeding at least once in surrounding many of the Drazi ships.
Sheridan orders the fighters to take point while the medium class ships provide escort. He manages to counter the Shadow flanking maneuvers, but the Alliance still loses many ships. Even the mighty Minbari Sharlin class war cruisers or the new, advanced White Stars could not equal the power of a Shadow Vessel.
At least two Shadow Vessels are destroyed and probably others are as well. Dozens of Shadows fighters and smaller craft are wiped out. The Vree saucers prove particularly effective at destroying the small Shadow ships.
Ultimately, the Army of Light was capable of driving back the Shadows, but at a very high cost, as for every two of their ships that were destroyed, one Shadow ship was destroyed.
The surviving ships took their wounded back to Babylon 5 or their respective empires for treatment, in addition to making repairs for their ships. This was the first time that all the League Worlds were organized into a capable fighting force.