After more than four months of fighting, Ukraine's counteroffensive is grinding on. There have been none of the rapid mechanised advances many Ukrainian allies hoped for. Instead, there has been a hard, grinding assault intended to slowly break into, and eventually through, the main belt of Russian fixed defences. Today I want to look at the way the counteroffensive has evolved over time, what we've learned about Russian defences and tactics, and what all of that might mean as months of mud and winter cold grow ever closer.