The long-awaited deal on the legal status of the Caspian Sea signed on Sunday in the Kazakh port of Aktau is a defining moment in the ongoing, massive drive towards Eurasia integration.

Up to the early 19th century, the quintessentially Eurasian body of water – a connectivity corridor between Asia and Europe over a wealth of oil and gas – was exclusive Persian property. Imperial Russia then took over the northern margin. After the break up of the USSR, the Caspian ended up being shared by five states; Russia, Iran, Azerbaijan, Turkmenistan and Kazakhstan.

Very complex negotiations went on for almost two decades. Was the Caspian a sea or a lake? Should it be divided between the five states into separate, sovereign tracts or developed as a sort of condominium?