Battle of the Helios Channel

The Battle of the Helios Channel was a massive fleet battle between the Confederation of Garman and the Gretian-Tyretian Empire on the 10th April 266, when a Garmanese fleet attempted to break through the Gretian Blockade and support Solitude.
The Gretian Fleet warned the Garmanese to turn around with warning shots. Official Gretian reports indicate the Garmanese opened fire on the Gretian fleet, the Garmanese report they opened fire in response. The battle lasted approximately two hours and saw the sinking of 29 ships, 16 Gretian and 13 Garmanese, including the flagship LRG Shallowspark, and serious damage to 14 more, 3 Garmanese and 11 Gretian ships, one including the Empress Elizabeth II's propulsion. 
The Battle had an unprecedented level of death and destruction, with massive losses for both sides, though the Gretians outnumbered the Garmanese, winning with overwhelming numbers and sustaining lighter losses.