The UK Carrier Strike Group (UKCSG) is a carrier battle group of the Royal Navy. It has existed in various forms since the mid-2000s. Between 2006 and 2011, the formation centred around the Royal Navy's Invincible-class aircraft carriers until the retirement of their Harrier GR9 strike aircraft in 2011 as a result of the Strategic Defence and Security Review. The UKCSG subsequently returned in February 2015 ahead of the entry into service of the new Queen Elizabeth-class aircraft carriers, HMS Queen Elizabeth and HMS Prince of Wales. The aim of the CSG is to facilitate carrier-enabled power projection.