On September 27, 2020, Azerbaijan launched a large-scale attack along the whole line of contact with the Nagorno Karabakh Republic. This was the third flare-up in Karabakh conflict in recent four years. In April 2016 Azerbaijan again launched an attack on Karabakh, however, hostilities were stopped after four days as a result of active Russian mediation efforts without any significant changes on the ground. In July 2020 clashes broke out along the northern part of Armenia – Azerbaijan international border. However, the September 2020 attack has few in common with both April 2016 four day war and July 2020 border skirmishes. For the first time since 1994 ceasefire Azerbaijan has been actively using hundreds of tanks, artillery, and multiple launch rocket systems, different types of drones, helicopters and combat aviation. Azerbaijani offensive is a well-planned operation, and the key directions of Azerbaijani attacks are towards the southern and northern parts of Nagorno Karabakh Republic. Another feature of this war is the active bombardment of all Karabakh cities, including capital Stepanakert. Another worrying sign is the active involvement of Turkey in combat operations. Turkey was always supporting Azerbaijan diplomatically in the context of the “One nation, two states” notion, and was one of the key suppliers of weapons together with Russia and Israel. However, this time Turkey’s role is unprecedented, as it includes the supply of modern Turkish “Bayraktar” drones, as well as sending F-16 fighter jets to Azerbaijan and active use of mercenaries from Syria alongside with regular Azerbaijani troops. This working paper analyzes the rationale behind the recent breakout of a long-expected military confrontation, the new dynamics to the old conflict as well as the role of Great Powers.