The speed of innovation on the Ukrainian battlefield means frontline troops may need a new drone design within weeks — but the country’s defense industry faces a critical labor shortage that threatens to derail that pace. Tens of billions of dollars in investments and wartime demand have fueled the creation of thousands of defense companies in Ukraine, but the supply of workers has failed to keep up. Yurii Faraponov, chief operating officer of Blue Bird Tech, said his company can’t respond to some frontline requests because he doesn’t have enough engineers.