Question: Why were the Panzer division commanders unable to move on June 6?
About the article "Invasion of Normandy", section "Armoured reserves".

Candidate passages:
Rommel's defensive measures were also frustrated by a dispute over armoured doctrine.
In addition to his two army groups, von Rundstedt also commanded the headquarters of "Panzer Group West" under General Leo Geyr von Schweppenburg (usually referred to as "von Geyr").
This formation was nominally an administrative HQ for von Rundstedt's armoured and mobile formations, but it was later to be renamed Fifth Panzer Army and brought into the line in Normandy.
Von Geyr and Rommel disagreed over the deployment and use of the vital Panzer divisions.
Rommel recognised that the Allies would possess air superiority and would be able to harass his movements from the air.
He therefore proposed that the armoured formations be deployed close to the invasion beaches.
In his words, it was better to have one Panzer division facing the invaders on the first day, than three Panzer divisions three days later when the Allies would already have established a firm beachhead.
Von Geyr argued for the standard doctrine that the Panzer formations should be concentrated in a central position around Paris and Rouen, and deployed "en masse" against the main Allied beachhead when this had been identified.
The argument was eventually brought before Hitler for arbitration.
He characteristically imposed an unworkable compromise solution.
Only three Panzer divisions were given to Rommel, too few to cover all the threatened sectors.
The remainder, nominally under Von Geyr's control, were actually designated as being in "OKW Reserve".
Only three of these were deployed close enough to intervene immediately against any invasion of Northern France; the other four were dispersed in southern France and the Netherlands.
Hitler reserved to himself the authority to move the divisions in OKW Reserve, or commit them to action.
On 6 June many Panzer division commanders were unable to move because Hitler had not given the necessary authorisation, and his staff refused to wake him upon news of the invasion.
In addition to his two army groups, The Commander-in-Chief West, Field Marshal Gerd von Rundstedt, also commanded the headquarters of "Panzer Group West" under "General" Leo Geyr von Schweppenburg (usually referred to as "von Geyr").
This formation was nominally an administrative HQ for von Rundstedt's armoured and mobile formations, but it was later to be renamed Fifth Panzer Army and brought into the line in Normandy.
Von Geyr and Rommel disagreed over the deployment and use of the vital Panzer divisions and so Rommel was unable to implement his preferred defensive plan because of a dispute over armoured doctrine.
Von Geyr argued for a conventional doctrine: keeping the Panzer formations concentrated in a central position around Paris and Rouen, and deploying them "en masse" against the main Allied beachhead when this had been identified.
Rommel, however, recognized that the Allies would possess air superiority and would be able to harass his movements from the air.
He therefore proposed that the armoured formations be deployed closer to the likely invasion beaches.
Although this dispersed the formations, he believed that it would be better to have one Panzer division facing the invaders on the first day, than three Panzer divisions three days later when the Allies would already have established a firm beachhead.
The argument was eventually brought before Hitler for arbitration.
He characteristically imposed an unworkable compromise solution.
Only three Panzer divisions were given to Rommel, too few to cover all the threatened sectors.
One, the 21st Panzer Division ("Generalmajor" Edgar Feuchtinger) was deployed near Caen as a mobile striking force as part of the Army Group B reserve.
However, Rommel placed it so close to the coastal defences that, under standing orders in case of invasion, several of its infantry and anti-aircraft units would come under the orders of the fortress divisions on the coast, reducing the effectiveness of the division.
Hitler designated the remaining seven armoured divisions, nominally under Von Geyr's control, as being in German Armed Forces HQ (OKW) Reserve.
Only three of these were deployed close enough to intervene immediately against any invasion of Northern France, the other four were dispersed in southern France and the Netherlands.
Hitler reserved to himself the authority to move the divisions in OKW Reserve, or commit them to action.
On 6 June, many Panzer division commanders were unable to move because Hitler had not given the necessary authorization, and his staff refused to wake him upon receiving news of the invasion. 
On 1 September 1939 the inventory of tanks assigned to the division was as follows: 15th Panzer Regiment *Panzer I: 57 *Panzer II: 74 *Panzer III: 3 *Panzer IV: 7 *SdKfz 265, SdKfz 267 and SdKfz 268: 9 31st Panzer Regiment *Panzer I: 80 *Panzer II: 63 *Panzer III: 0 *Panzer IV: 6 *SdKfz 265, SdKfz 267 and SdKfz 268: 11  
The 9th Panzer Division's final combat assignment came in a battle near Cologne on March 6, as a part of the battered LXXXI Corps, alongside the 363rd Volksgrenadier Division and the 3rd Panzergrenadier Division which were in equally poor shape, and the entire corps was barely the strength of one division.
Facing them was the US 3rd Armored Division.
The division attempted to defend the town from attack, but was unable to make progress against American forces.
After its unsuccessful attack, the shattered 9th Panzer Division was counterattacked by strong Allied forces.
The division engaged the Americans in the city center of Cologne, but were quickly pushed back, and the divisional commander was killed.
Remnants of the division attempted to flee across the Rhine River.
In the fighting that followed, the weak formation finally collapsed.
Most of the remains of the division were forced into the Ruhr Pocket, continuing to suffer staggering losses while holding lines on the south flank of Army Group B until they surrendered to American forces in April 1945.
By this time, the demoralized soldiers of the division were entirely out of ammunition and gasoline, and remaining troops surrendering without a fight.
The division continued to exist briefly afterward; Major Halle, the division's adjutant, escaped the Ruhr encirclement with a small battle group, and joined the 11th Army in the Harz Mountains.
There, on April 26, 1945, German commanders of OB West disbanded the 9th Panzer Division, absorbing its survivors into other units. 
The Battle for Caen.
Operation Neptune.
The first operation intended to capture Caen was the initial landings on Sword Beach by the 3rd Infantry Division on 6 June.
Despite being able to penetrate the Atlantic Wall and push south the division was unable to reach the city, their final objectives according to the plan, and in fact fell short by .
The 21st Panzer Division launched several counterattacks during the afternoon which effectively blocked the road to Caen.