It is a December morning in Kupyiansk, some 120km (75 miles) south-east of Kharkiv, and the temperature is -7C, even before the howling wind hits you and finds its way into every inch of loose clothing or exposed skin. It is mostly open ground - there is no cover from the wind, nor from the Russians who in places are within rifle range. Lines of trees, which in the summer provided camouflage, are now stark and bare. There is nowhere to hide.