Deep in a birch forest on a hot May morning, our rattling 4×4 comes to a crunching halt, a small cloud of sandy dust rising around it as we step out. It takes a few moments — and a quick check of our GPS tracker — to make sure we’re in the right place. Off the path, to the right, obscured in the undergrowth, branches pulled across its roof and sides, is another vehicle. We walk around it, and rap on the doors at the back.Colonel Eero Rebo, 42, leans out from the dim interior in which half a dozen other Estonian ­soldiers crouch around radio sets and the faint blue glow of LCD screens. The colonel’s face is thick with camouflage paint. He swings his legs forward and jumps down with a heavy thud to the ground. We walk a little way into the forest.

“They will use their armour to try and break through this afternoon,” he says, sketching out the outline of his battleplan somewhat warily as he eyes the smartphone I am using to record our conversation (but which provides an easy target for signals intelligence). “And I will use the terrain — the rivers, the forests — to stop them. I will get them into areas where they are weak but I am strong.”