Sheldrake wrote:
1. The German decision to invade the Soviet Union was based on the over confident assumption that the USSR would collapse within three months. The lack of motorised field and medium artillery tractors capable of coping with Russian conditions is just one of many deficiencies.
This is true, but the point of a "What if" is to discuss alternate possibilities.
2. The German motor industry did not have the capacity to build enough trucks to motorise their army in 1935-1939. Motoring the divisional and medium artillery would be at the expense of motor vehicles for something else. One option was to leave the anti tank battlaions of infantry divisions and companies of regiments with horse drawn anti tank guns. Some German general advocated this in their memoirs IIRC. This would have denuded the German infantry of the motorised elements often used as the advance guards in 1941.
There were companies in Germany that went under utilized. For example, to get the say, 5,000 tractors to motorize artillery would have actually been rather easy. The Wehrmacht simply orders them from Lanz Bulldog, a manufacturer that already produces such a machine. Thus, a manufacturer that is being under utilized would be making many of the tractors used.
Hanomag was also manufacturing tractors. They quit early in the war because the Wehrmacht wanted them to concentrate on other production.
http://tractors.wikia.com/wiki/Lanz_Bulldog
Lanz produced a crawler tractor starting in 1934 that would have been suitable. Most of their line were diesel or semi-diesel engine machines and were noted for their simplicity and ease of maintenance. A yearly production of say 750 to 1000 would hardly have strained their pre-war resources given that Lanz produced tens of thousands of tractors from the 30's to the end of the war.
I suspect that it's more a case of the Wehrmacht's officers and procurement people being loath to use what is a simple agricultural tractor for military purposes that kept it from being used.
Oh, I did find a few interesting photos along the way researching this:
That rarity of German construction machinery:
A Lanz Bulldog crawler tractor bulldozer!
And the wheeled version:
And, it's apparent that of those manufactured some did end up in military service