What is meant by the “decline of the Westphalian system”?

As for the Westphalian system, its essence was that none of the countries should have advantages in forces that surpassed the power of possible rivals. This system constituted the principles of international relations. According to them, the great powers were supposed to function. The main principle was considered the principle of national state sovereignty. According to him, any state should have full power only on its territory. The decline of the Westphalian system meant the termination of all the established principles of international relations due to wars and revolutions that continued to occur during the operation of the described system.