Washington: In describing how nasty the Washington-Moscow relationship has become, analysts are reaching back a full century, to the Bolshevik Revolution and the ensuing Russian Civil War, when the US embassy in Moscow was shuttered for 15 years.

The Cold War imposed a manageable, if at times frightening, diplomatic dynamic.

But Moscow's weekend confirmation that the US must cut its embassy staff by 755 comes as the two powers butt heads in the Middle East, as tensions mount on the Korean Peninsula and the Ukraine crisis festers. All are unfolding with none of the guard-rail certainty that endured for more than four decades after World War II – and with both countries led by unpredictable, headstrong presidents.

As Vladimir Putin warned of possible further Russian measures against the US, the Trump administration was flexing its military muscle over the Koreas – flying two supersonic B-1 bombers over the peninsula with Japanese and South Korean aircraft along for the ride, at the same time as the US responded to a new North Korean missile test with its own missile defence test over the Pacific – which it claimed was a success.