The late Soviet fleet struggled to fill its middle tier

The Soviet Navy repeatedly struggled to provide the medium ships between its largest combatants and smaller vessels. High and low capability mean different things in different threat environments. In the World War II comparison, sloops occupy the low end of a low-threat setting, while destroyers and cruisers occupy intermediate positions and capital ships sit at the high end of a dangerous one. The middle ship must serve as the stronger vessel in routine operations and the lesser unit in a major force. The mix therefore concerns efficient operational use as well as cost. Danish use of interchangeable StanFlex components provides a brief example of using common ships for different tasks.