After the Trump administration has halted military and economic support to Ukraine, what can Ukraine do to ensure a sustained war effort? This column describes how Ukraine’s wartime economy faces these challenges: (1) limited productive capacity and power generation that are constantly under Russian attack, (2) large fiscal deficits, and (3) large external trade deficits. Foreign aid is the best solution to these challenges, but if external aid does not materialise, Ukraine will have to mobilise resources internally to cover military spending over a long period of time. The authors discuss policies for this contingency. […]