While I am on vacation, please enjoy this outdated fact from The Universal Databanque: A Compleat Encyclopaedia Of Doctor Who For The Exhaustively Nerdy, 2011 Edition:
Arcadia – A planet in Mutter’s Spiral which became entangled in the Time War. Arcadia was similar to Earth of the early twentieth century, but lacked Earth’s propensity for warfare. Zodin the War Queen infiltrated Arcadian society to stoke nationalistic impulses in order to advance Arcadian technological development. Her interference led to the planet’s first global war. Visiting Arcadia during this time period, the Doctor first became aware that the War Lords had become active again [PDA: Codicil]. Arcadia was rich in Kontron Crystals, which allowed them to rapidly develop space travel. The ninth Doctor, unaware of the role Arcadia was to play in the war, intervened to delay their development of Time Travel, believing Arcadian culture was not ready [HV: The Rise of Arcadia]. Some Arcadians became aware of the interference of the temporal powers in their history and successfully petitioned the Time Lords to establish a defense pact. Arcadia became strategically important for much of the war as the War Lords sought to capture the planet for its resources. In an attempt to extract the planet from the war, the tenth Doctor caused a chain reaction rendering most of the Kontron crystals inert [HV: The Siege of Arcadia]. However, this backfired when the Time Lords deprioritized the planet’s defense, leading to its devastation by a surprise War Lord attack [HV: The Fall of Arcadia]. Witnessing the fall of Arcadia prompted the eighth Doctor to pursue the Pandorica in order to end the war once and for all [BF: Other Wars]. Varnax was an Arcadian military leader who was allied with the Doctor prior to his corruption by the War Lords [WDA: The Ancestor Cell].