The CSTO charter reaffirmed the desire of all participating states to abstain from the use or threat of force. Signatories would not be able to join other military alliances or other groups of states, while aggression against one signatory would be perceived as an aggression against all. To this end, the CSTO holds yearly military command exercises for the CSTO nations to have an opportunity to improve inter-organization cooperation. A CSTO military exercise called "Rubezh 2008" was hosted in Armenia, where a combined total of 4,000 troops from all seven constituent CSTO member countries conducted operative, strategic and tactical training with an emphasis towards furthering efficiency of the collective security element of the CSTO partnership. The largest of such exercises was held in Southern Russia and central Asia in 2011, consisting of more than 10,000 troops and 70 combat aircraft. In order to deploy military bases of a third country in the territory of the CSTO member-states, it is necessary to obtain the official consent of all its members. It also employs a "rotating presidency" system in which the country leading the CSTO alternates every year.