Russia's apparent suspension of plans to deploy missiles in its western enclave of Kaliningrad is an olive branch to the Obama administration. In practical terms, it changes little. But the move may open a new chapter in the tortuous history of missile defence between the two biggest nuclear powers, dating from their 1972 Anti-Ballistic Missile Treaty. By limiting missile defences on each side, that treaty enshrined the nuclear balance of terror – Mutual Assured Destruction, or MAD.
The first threat to it came in 1983 with Ronald Reagan's Strategic Defense Initiative ("Star Wars") – a space-based missile system using technology he even offered the Soviet Union. But SDI was impractical, and the US shifted to limited missile defence against rogue states that might go nuclear, such as North Korea and Iran. All along, Republican administrations have been keener than Democrats.
George Bush Snr pressed ahead with it when president but funding and testing were cut back under Bill Clinton. George W Bush revived missile defence (as "a theology", according to a leading Democrat). Spending rose to $10bn (£7bn) a year, even though test results were mixed. To free US hands, Mr Bush withdrew from the ABM treaty in 2002. He then accelerated plans for anti-missile sites in Alaska and California – to counter any North Korean attack, and in Poland and the Czech Republic – to defend against a launch from Iran. But this latter project, with US missiles in the former Soviet satellites, enraged Moscow, which believed they were aimed more at it than Iran. In vain, Washington sought to convince that was not so, arguing the few missiles deployed would be overwhelmed by any Russian attack.
Immediately after Mr Obama's victory, Russia announced Iskander missiles would be deployed in Kaliningrad, bordering Poland. Now, however, it may believe the new Democratic president, faced with huge spending constraints, may follow Mr Clinton making missile defence a lesser priority. It would be a signal Moscow is ready to talk.