Modern wars are won by grinding, not by genius
Actually, they are won by both:
Look up the details of how Stalin passed the complete plans for Operation Mars to the Germans as cover for Operation Uranus (the Stalingrad counter-offensive) and thereby also established complete trust in a Soviet double agent, whose subsequent feeding of a mixture of good and bad information to the Nazis was important to the rest of the conduct of the war.
Or consider how the Cold War (by your leave, WW III, just fought in slow-motion thanks to nuclear deterrence) was won.
It's just that genius must now be applied at the strategic, rather than operational or tactical level, to be decisive.