NATO member states sought to put together a show of unity despite ongoing tensions at the alliance's recent 70th anniversary meeting in London, but discordant voices arose on several issues ranging from funding to the nature of NATO.

Ahead of the summit, French President Emmanuel Macron said that NATO was "brain dead". The statement caused controversy, but at the summit he said that he stood by his words.

Professor Joav Toker from the American Graduate School in Paris backed Macron's view and stressed the urgency for NATO to define its adversaries 30 years after the fall of the Berlin Wall.

For Mark Pinner, China practice managing director from Interel Consulting, "brain dead" was a veiled way of calling for change as well as Macron's agenda to create an European army.

"One of the big issues on its (NATO's) agenda is what NATO's mission is. Clearly, President Macron wants to redefine it. He wants to have a new mission where NATO focuses more on terrorism and issues in Africa and less focuses on military threat from Russia," said Pinner.

Cui Hongjian, director of the Department for European Studies at the China Institute of International Studies, agreed with Pinner that one of the key issues for NATO is to establish a consensus on the major threat to most of its members, if not all.

He further pointed out that as early as the end of the Cold War, NATO, a collective military organization, has been trying to find the reason for its survival. Right now, this is even more critical amid the U.S.' changing policy towards Europe.

He also referred to NATO Secretary General Jens Stoltenberg's remarks on transferring NATO from a military organization to a both political and military one as a familiar idea — in fact NATO tried to change its nature as a military organization a few years ago.

As the core NATO principle, the concept of collective defense as defined by Article 5 of the 1949 Washington Treaty establishing the alliance states that "an armed attack against one or more of them in Europe or North America shall be considered an attack against them all."

However, with U.S. President Donald Trump's "America First" agenda and shifting policy in Syria, the European allies are becoming more concerned about security issues in North Africa and the Middle East, making NATO's core principle of Article 5 a point of contention among its members, concluded Cui.

"Dialogue with Yang Rui" is a prime time English-language talk show on CGTN. The 30-minute program covers a wide range of domestic and international topics, providing a balanced and critical perspective on current affairs and analysis within the framework of cross-cultural and multi-disciplinary comparisons.