America returns to containment to deal with Russia and China

The air strikes that pummelled the Ukrainian military base near the town of Yavoriv early on Sunday were notable not just because they killed some 35 people, nor even also because they expanded hostilities to the far west of Ukraine, a region previously largely unscathed by Russia's invasion. Most important, the base, ironically named the International Peacekeeping and Security Centre, had been used until recently by America and other North Atlantic Treaty Organisation countries to train Ukrainian troops. It is a mere 18km from Poland, a Nato member, and has become a staging post for the weapons and other supplies that Nato countries are funnelling to Ukraine.

For those who fear the war may expand beyond Ukraine's borders, the attack was the most worrying evidence yet. For Western leaders, especially, it was a reminder of the difficulty of preventing their confrontation with Russia from escalating.