Russia’s intervention in Georgia proved to be the spur that drove the US to strike a deal with Poland to build part of the missile defence shield on its territory, an accord that will be signed by Condoleezza Rice, US secretary of state, in Warsaw on Wednesday.

For months, US diplomats sought to avoid exacerbating Moscow's considerable irritation over the missile programme by only agreeing to the missile shield – which has little practical benefit to Poland. The missile defence programme is intended to counteract a threat from Iran, not Russia. But Poland sought Patriot missiles too, not so much as an effective defence but more as a symbol of US solidarity. US agreement to this represents unambiguous support for Poland amid Russia’s new assertiveness.