Some other tips to keep in mind when combining/retraining. If you have depleted troops with armor/weapons upgrades, you should restock them with the highest-valor replacements possible. Sometimes that'll be other upgraded (or not) troops that have gained valor in combat, but often you can built the same type of troop without the hardware upgrades but with a valor bonus (province or master-level building bonuses). Those are the best kind to feed into your upgraded partial units.