How Russia is holding Ukraine’s wheat exports to ransom

Starvation is a weapon as old as war itself. But Vladimir Putin has put a perversely postmodern twist on the ancient stratagem. Instead of menacing his Ukrainian enemy with hunger and poverty, he is threatening the whole world. Putin has long used oil and gas as a political instrument, most recently cutting off supplies to Poland and Bulgaria in retaliation for their refusal to pay their bills in roubles.