If they were brought into operation, multiple things could in theory go wrong with these weapons. For one thing, the delivery systems themselves might not be reliable. Mark Schneider, formerly of the US Department of Defense’s senior executive service, has written about the many problems Russia has faced with its missiles so far during the war with Ukraine. Last spring, US officials said between 20 and 60 percent of Russian missiles were failing, either in terms of not launching or not hitting the intended target.