While Russian manpower inside Ukraine declines, the Ukrainians are seeking to train the many volunteers that joined the military after the invasion. Even with losses from six months of fighting, there are still nearly 700,000 of these volunteers. Most require training before they are up to the standards required for a successful offensive to push the remaining (under 200,000) Russian forces out.
Even before the invasion, NATO had been assisting in training Ukrainian forces. This accelerated after 2014 and by the end of 2021 most of the Ukrainian 200,000 troops were adequately trained. These troops suffered heavy losses in the first six months of the war and must now be supplemented by trained volunteers. There was little formal training for volunteers in the first few months of the war. Weapons were distributed and training was often on-the-job.
Being on the defensive requires less skill and experience but does benefit from enthusiasm and steadfastness. Still, casualties were high, especially when the Russians were using a lot of artillery. Trained troops know to quickly disperse and dig in, not just in trenches and foxholes but also with sturdy overhead cover.
Part of the NATO support was offered to conduct training outside of Ukraine. Some were carried out in Poland and more distant locations like Britain. There were language barriers and some of the training outside Ukraine was for new weapons systems. The Ukrainians proved to be quick learners and mastered technical skills in days that conventional military training programs spent weeks on. That urgency and motivation is what still propels Ukrainian volunteers but, for offensive warfare, a lot more skills must be acquired.
To do that NATO nations are expanding their training programs and allocating some of those efforts to teach experienced volunteers how to operate basic and advanced military training inside Ukraine. This would involve shorter, more intense training programs that are possible if the trainees are eager to do it and do it well. Even with all this it still takes several weeks to turn an untrained volunteer into a trained soldier with some of the essential skills needed to carry out offensive operations that are not suicidal. In other words, the volunteers how to avoid fighting like Russians.
Going on the offensive unprepared is not good for maintaining morale and enthusiasm. Two key elements of a successful offensive are competent staff and senior officers to plan and organize the offensive operations, and competent junior officers and senior NCOs in the combat units to carry out the plan effectively. Senior officers and planners Ukraine has, but there is a shortage of NCOs and lower ranking officers needed to lead platoon (30-40 men) and company (three or four platoons) units. The infantry has always suffered most of the casualties and the number of casualties those are depends on the quality of training, leadership and support (artillery, intel on the enemy and good communications). The support is there, the major weakness continues to be training levels and shortages of NCOs and combat unit officers.
Ukraine has also been quietly devoting a lot of resources to supporting the armed resistance in Russian occupied territory. Ukraine already had an effective special operations force. These capabilities were demonstrated after 2014 when Ukrainian special operations were responsible for foiling Russian operations in Donbas. Work was already underway to carry out covert and sabotage missions in Russian occupied territory but that was difficult because Ukraine was not actively trying to take back Crimea and Donbas until after Russia invaded all of Ukraine in 2022. It took about six months to recruit, train and organize attacks on Russian bases, Russian officials and Ukrainian collaborators. This lifts the morale of the Ukrainian troops preparing to go on the offensive.
Even with active partisan and special operations forces attacks in occupied territory, the offensive operations will be carried out gradually until more trained units are available. This disappoints many Ukrainians, but less so the closer you get to the front lines. The troops understand but the general population continues to suffer from Russian attacks with missiles and unguided rockets on infrastructure and cities. The Russians do this on purpose because if they can damage civilian morale, it will have an impact on the outcome of battles.