To anyone standing on a hilltop in Lysychansk, it is clear why this city that is soon to be the focal point of Russia’s offensive in Ukraine’s east seems defendable: it’s on high ground. Across the sprawling plains of Ukraine’s Donbas region, which is home to Lysychansk, elevation is a rarity, leaving the city’s Ukrainian defenders in an advantageous position. But it will be impossible to defend Lysychansk, whose pre-war population was around 100,000 people, without a way to get in the necessary supplies: ammunition for Ukrainian tanks and artillery, food and equipment for the thousands of troops garrisoned there.