Three facts stand out as clear after Russia¡¯s arrest of the alleged perpetrators of Friday¡¯s appalling terrorist attack on Moscow¡¯s Crocus City Hall concert venue ¡ª and all three shine a light on dangers inherent in the new multipolar world we live in.

The first is that Russian President Vladimir Putin had dismissed the United States¡¯ earlier warning that the attack was coming, both in public and to his top security officers. He labelled American intelligence that Islamists were planning an assault on a large Russian venue as blackmail, aimed at destabilizing his country ¡ª a vague notion that he did not explain.

There was a time not so long ago when Putin understood that Washington considered Islamist radicalism as a shared threat, one taken so seriously that it was ring-fenced from other disputes. The Russian president would have heeded the warning, even if he could not prevent the attack.