Combined arms operations. Test of the officer corps

The German army in WWII showed the world the power of combined arms, infantry, with artillery support, tank support, air support.  It was potent enough to crush the French, largest army in Europe in 1940, an army that had stood off German attacks for four years just twenty years earlier.  The Anglo Americans needed a year of combat experience in North Africa to learn how to do it. 
   Doing combined arms operations is complicated.  To order a single infantry or tank unit into action is simple, give them the objective, and the time and date.  Then it's up to the unit commander to bring his men into action.  Not too hard. 
   Now consider doing an operation with artillery support.  You want the guns to shell  enemy positions until your men reach them.  Then you want to "lift" the barrage to strike enemy rear areas while your men assault the front line positions.  You have to order the artillery units into position, and make arrangements to get tons and tons of shells up to the guns.  You have to coordinate with the artillery, make sure that both artillery and infantry are using the same maps of the action.  You have to make sure that both the artillery and the infantry know just where the attack is going in, and especially when the attack goes in.  Before the introduction of walkie talkies in WWII, the timing was the Achilles heel.  The attack usually was late, for any one of a number of reasons, and there was no way for the artillery to know this.  So they would lift the barrage as scheduled, even if the infantry was hours from making contact with the enemy.  Once the infantry had walkie talkies to control the artillery things got a lot better. 
   Tank support was not as complicated as artillery.  Order the tank unit[s] to attack at the same time as the infantry.   Make sure the infantry is knows the tanks are friendly tanks, lest they start pot shotting them with bazookas. 
   Air support can be tricky.  The aviators, especially single seat fighters, are never all the sure where they are.  It's real easy to get confused and bomb your own forces.  This happened repeatedly.  The best of coordination, aerial photos of the target area, special marking on friendly vehicles, and forward air controllers will improve things. 
   Getting all this stuff right is what you have officers for.  If they don't get it right, they are apt to loose the battle. A division commander who could put all this together and get it right was a rare asset.