In recent years, German historian Sönke Neitzel and American military historian Steven Zaloga, amongst others, have examined the combat performance of highly decorated German tank crews during the war. Zaloga argues that "Panzer ace" is a romanticisation of reality mixed with propaganda, as it is neither possible to correctly determine "tank kills" in the heat of the battle nor to separate individual performance from technological or battlefield advantage. In contrast, British historian Robert Kershaw argues that the large number of tanks destroyed by some German commanders can be attributed to the skills they gained through years of combat.