$   German Wehrmacht applied a multi-level commanding system.  The supreme commander post was held by$
$Adolf Hitler - Fhrer and Chancellor of the Third Reich.  His direct subordinates were commanders of the Army$
$(Oberkommando das Heer), Air Forces (Oberkommando der Luftwaffe) and the Navy (Oberkommando der Kriegs-$
$marine).$
$   The commander-in-chief of the Army (gen. col von Brauchitsch) had under his command two Army Groups:$
$Army Group North and Army Group South.  The first one consisted of 3rd and 4th Armies.  Army Group South$
$consisted of 8th, 10th and 14th Armies.  Every army consisted of corps of various types (infantry, armoured$
$and motorised corps).  Army corps contained two to three divisions of the same kind.  There were also$
$reserves available on every level.  They included infantry, heavy artillery and long range reconnaissance$
$aircraft.$
$  Air force was divided between 1st and 4th air fleets (Luftflotten).  Air fleets consisted of fighter, bomber$
$and diving bomber wings.  Wehrmacht and Luftwaffe operations were co-ordinated by liaison officers. The rules of$
$co-operation between air and land forces were constantly improved.  It became almost perfect during$
$the campaign in France in June 1940, when aerial support for the armoured spearhead could be summoned$
$by a single phone call.$
$  Because of the clear division of competence German commanding system was highly effective on every level.$
$Well organised aerial reconnaissance assured that commanders usually had actual information of enemy forces.$
$The only serious mistake was made in case of "Poznan" Army forces.  Assuming that Polish detachments$
$disembarking from trains in Skierniewice belonged to "Poznan" Army evacuated from Wielkopolska (in fact,$
$there were units of "Prusy" Army), German commanders allowed dangerous stretch of the 8th Army columns$
$turning the "Lodz" Army flank.  This way the 8th Army flank became dangerously exposed for a strike.$
$The opportunity was exploited by the Poles, who delivered a blow against the German army at Bzura river by$
$"Poznan" Army forces. That incident didn't influence the outcome of the campaign, although caused some$
$confusion in German HQ's$
