The battle of Wolf 359 refers to first ever large-scale major battle in 2367 between Starfleet and a single Borg cube. Starfleet mobilized a fleet of fourty starships which under the command of Admiral Handon engaged a single cube unexpectedly commanded by Locutus (aka Jean Luc Picard) following his earlier assimilation whom unwillingly provided the Borg with tactical information from his years of experience, knowledge and familiarization with Starfleet technology providing the Borg with a devastating advantage. As a result 39 of the fourty vessels were destroyed resulting in over eleven thousand deaths. After annihilating Earth's defense force the cube proceeded towards Earth, quickly breaching the Mars Defense Perimeter by defeating the small force present there and took up position in Earths orbit in preperation to assimilate humanity.
The Enterprise-D had managed to re-capture Locutus and with the assistance of data use his uplink to the Borg cube to input a command to perform a regeneration cycle and power down. An away team aboard the Borg cube descovered a power feedback caused either deliberately as a form of self-destruct or as a result from an early regeneration cycle resulting in the destruction of the Borg ship.