I read random descriptions of Germany's attack on the Soviet Union, and I got the impression that besides tanks, the armies carried with them millions of horses and that the bulk of the soldiers were planned to reach Moscow and Caucasus on foot (which is really a feat even for a tourist).
Is my impression correct?
You are correct. Parts of the Wehrmacht were mechanized, but the vast majority was foot infantry with horse drawn logistics. Most soldiers walked towards Moscow, and back.
When the Wehrmacht arrived in Prague in March 1939, it was a bicycle army. The same role as USA trucks played for the Russian army in 1941-45 was played by the Czech Skoda and Tatra cars and trucks for the German army.
After the Allied invasion in Normandy the Wehrmacht had moved all motorized groups to the West and only usual infantry remained in the East. That made the huge encirclements of 1944 on the Eastern Front possible. Whole regions and republics occupied by non-mobile German troops were cut off one after another. With these troops, they couldn't even escape in time.
(It was after the Soviets reached the German lands themselves when the point of German power was turned back to the East.)
So, we can't say if the German army was motorized or not without asking what time and place we mean exactly. One of the strengths of the German and Soviet generals in WWII was that they could change not only the size and concentration of troops dynamically, but also their level of modernity. There were places where the maximally modernized and mobilized troops fought, and tens of kilometers away there were troops that looked like their WWI counterparts. Continental countries did not get the fantastical amount of technological equipment that the US army had, and they concentrated that equipment in important locations only. And as the Ardennes showed, it was more than enough.
There is another problem - motorized HOW? For example, while Stalin was preparing to the WWII in Europe in 1940-41, USSR was building "highway tanks" - with great speed, but for good roads only. But in the USSR itself there were no good roads. Even in 1989 my German far relative, a roads specialist, when he visited us in Moscow and looked around the capital, said: I haven't seen roads here, but there are places where I can drive a car. One of my acquaintances - an old Soviet officer who went by foot from Russia to Germany during WWII, had said, that along their way in all the USSR they crossed only one paved road and one asphalted. I do not remember the latitude of his way, but the main thought remains - cars in the USSR had limited use.
And in some seasons they were of no use at all. The asphalted road to Astrakhan - a regional center on Southern Volga - was built in year 1981. And before that every autumn and spring the usual ground road became unpassable. The only transport that could be used was special trucks for strategic rockets, with an engine in every wheel. And they had to travel in pairs, to help each other in harder places. (The ground is so sticky there, when wet.) In 1945 the car that could pass any Russian road simply didn't exist anywhere in the world. Even in the 90ies they said in Russia: Jeep is a car that will stuck where no other car can reach it. Another Russian proverb: Russia has two problems: fools and roads.
So, on the Eastern front it was different - tanks could run, but not too far, and with cars and trucks sometimes you had lesser speed than without them. The railway theme, raised by Michael Kay, was of extreme importance then. But the railroad mobility was not defined by the modernity of the army, but by the number of roads on the land and their defense from the air and partisan attacks.
Very important and heavily underestimated by both sides was also the river transport. Dnepr, Bug, Dnestr, were much more powerful than any rockade way.
No-one has mentioned trains. While there was a lot of walking, there was also a lot of bulk movement of troops (and supplies) by train.
Just barely. Only 20 (out of about 190) divisions were Panzers, with a slightly smaller number of motorized infantry divisions. So the Wehrmacht was only about 20% mechanized and motorized. That's less than either the American or British armies and even the Soviet armies (after Lend Lease kicked in during late 1942 and later).
"Most" German soldiers marched on foot, with their supplies being drawn by horses. That caused problems around Moscow during the first winter, and contributed to the shortage food (lack of accumulated surpluses before the encirclement) at Stalingrad.
It also contributed to problems on the Russian front. Around Smolensk, and in certain parts of the Ukraine, a portion of the Soviet armies escaped encirclements because the infantry could not move up quickly enough to fill gaps left behind by fast moving armored divisions. When they were on the retreat, the Germans were at a clear disadvantage. During Operation Bagration in 1944, for instance, the Germans inflicted physical casualties (killed and wounded) on the Russians at the rate of 2 to 1, but the Russians captured enough Germans to reduce to total casualty rate to 3 to 2, because the Russians had trucks (from Lend Lease),the Germans didn't, and stranded a large number of prisoners.
You're right. Wehrmacht was mechanized. Wehrmacht in 1941 was an ideal military machine. He had fast tanks and tractors. Tank and motorized divisions were all "with a motor". The motorized division could have only one company on Hanomag, but both regiments of infantry were necessarily transported by trucks. All transport provided a high speed of movement along the highway. Armored cars and radio communications allowed to react quickly to tank fists. This is also the speed of the division! A large number of sappers made it possible to quickly build bridges (see the encirclement of Kiev). This is the same speed division! Each German tank company had a repair truck, supply trucks and scout motorcyclists. This is the same speed division! The advanced German forces were supplied by air. This is the same speed and strength of the division!
Horses. This is the basis for the supply of infantry divisions. They were slow. And the infantry did move on foot. For example, in the German infantry company there was a horse for transportation of ammunition. Just like in the Soviet company. But even here there is a brilliant moment. German generals formed mobile groups in the infantry division. The mobile group is reconnaissance armored vehicles, self-propelled units, an infantry battalion on trucks and a battalion of howitzers. As a result, the advance of the infantry division moved like a tank division. Moreover, self-propelled units fought no worse than tanks and confused Soviet commanders. Soviet commanders did not understand, "if an infantry division is near, where did the tanks come from?"
At a strategic level, tank groups were stronger than Soviet mechanized corps. The Soviet mechanized corps had many tanks, but could not fill them. The German tank group (actually the tank army) had artillery and infantry. And this artillery easily destroyed mechanized corps.
The problem of the Wehrmacht in Russia was expensive: there were few roads, roads were bad. Plus the terrible weather.
The Western military machine is special forces + specialization + supply. Supply = big logistics. And this was the Achilles' heel of the Wehrmacht. The Wehrmacht received supplies problems already near Moscow. If the Wehrmacht retreated, the roads turned into a crowd of stuck trucks. When the trucks were destroyed, the Wehrmacht became very weak.
A little joke. How did the Soviet fighters fight the German Tigers? Very simple! A column of trucks and gasoline tankers supplies one Tiger. One Soviet fighter turns this column into a big fire. As a result, the invincible Tiger stands with empty fuel tanks and without shells. Checkmate.
Where was the Wehrmacht stronger than the Red Army? In the Soviet divisions there were fewer trucks. Moreover, they were less than the regular number (10-50%). In the Soviet motorized division very often the infantry moved on foot ... Soviet artillery moved slowly (tractor speed - 10 km/h). Soviet trucks were not all-wheel drive. Soviet industry produced very few heavy trucks. Bad communication: many divisions had only telephone communication with the headquarters of the front. As a result, the Soviet command reacted "slowly." In the Soviet tank brigade, the radio was only for commanders of battalions. Even reconnaissance of tank brigades was often without radio. There was never a truck in the Soviet tank company. The tank was repaired by the crew of the tank. The tank was in repairs of the tank crew. It takes time. The repair truck was only at the level of the tank brigade. Soviet tank units in 1941 had 4-5 types of tanks (different spare parts) and required 3-4 types of fuel. This is the suicide of logistics and the death of a mechanized corps.
Where was the Wehrmacht weaker than the Red Army? German troops demanded a lot of good roads. During the retreat, trucks blocked roads-a supply collapse. The Wehrmacht could not act autonomously when the supply was destroyed. German quartermasters often made mistakes: winter clothes were sent to Africa, condoms to Stalingrad.
My words: "Soviet commanders did not understand, "if an infantry division is near, where did the tanks come from?""
– Konstantin Nov 10 '17 at 13:07