Russian forces this week seized three Ukrainian naval vessels in the Sea of Azov of Crimea, the territory Russia forcibly annexed in 2014.
Moscow claims these are Russian waters.
But a 2003 deal between Moscow and Ukraine agreed the Sea of Azov would be Shared.
Ukraine warns its black sea ports are being cut off.
A bridge built by Russia linking it with Crimea now limits the size of ships able to navigate the Kerch Strait.
The aim is to change the facts on the ground part of the Kremlin strategy of stress testing the West, says the co-author of the strategic survey .
Report Nick Redmond.
Testing tolerances are probing for weaknesses, getting a measure of the resolve of other states by acts that are generally aggressive but below the threshold of something that would obviously require a military response.
The IISS report describes a contest between settled vs. Challenger powers.
Iran is also accused of conducting tolerance warfare using the Revolutionary Guards Corps and proxies across the Middle East to destabilize other countries like Syria.
Beijing’s activities in the South China Sea are also seen as part of a strategy to test Western resolve in that arena.
China has used not its Navy but says its Coast Guard or some other at water capabilities in order to slowly push the envelope in the South China Sea.
And I don’t see the island building campaign and then the the growth of infrastructure around.
There is about without directly confronting anyone nevertheless changing facts on the Ground.
So how should those on the receiving end of Tolerance warfare respond?
Redmond cites Britain’s reaction to the attempted chemical poisoning of a former double agent Soyal earlier this year which London blamed on the GRU, the intelligence branch of Russia’s armed forces.
What we saw was a powerful asymmetric response sanctions, tremendous degree of Allied solidarity over diplomatic expulsion and then an information operation overseveral months to systematically expose GRU activity.
The report’s authors say a new era of geopolitical competition urgently requires new rules governing international behavior but negotiating such a global framework is fraught with difficulty.
Henry Ridgwell for VOA news London
美国之音，伦敦，Henry Ridgwell 报道