The conflict in Ukraine, since Russia's full-scale invasion, is the worst war this continent has experienced since World War Two. Europe has relied on US military aid to help Ukraine, but those days of American largesse are expected to be over as soon as Biden leaves the White House. Even if Democratic candidate Kamala Harris becomes the next US president, Congress is thought likely to pivot to other foreign policy priorities. Germany's planned military revamp has got bogged down in bureaucracy, and there are concerns about European resolve and spreading 'Ukraine fatigue' among allies in Europe. Ukraine is in a particularly vulnerable moment, and extra help from its biggest backers cannot come fast enough.