The Campaign of Roses

The Campaign of Roses was a several month long crusade in which Sylvari forces (under the command of Oberon executed several hundred Moon Elves, both military-affiliated and civilian . Show Spoiler

Oberon's intent with The Campaign of the Roses was to re-establish his strength in Titania's eyes as he had grown violently jealous of her relationship with her adopted daughter, Queen Illyria of the Winter March 

The lasting effects of this event can be seen in the Sun Elf population outnumbering the Moon Elf population 3:1 to this day, as The Campaign of Roses pre-dates (and largely influenced) The Dragon-Sear .