After the Polish campaign Himmler won permission from AH to increase the number of SS divisions from 1 to 3, and to this task he devoted much of his energy during the Sitzkreig. They were to be difficult months for he encountered many restrictions in his freedom to recruit, some imposed by his own strict code of selection, but most by the army which had in the Reich conscription laws a powerful weapon to thwart his efforts.
These laws laid down that no German of military age could join the armed services until the local military registrar had given him clearance, a process which was governed by an adjudication between the manpower demands of the three branches, Heer, Kreigsmarine, and the Luftwaffe. The proportion of recruits each was allotted fell roughly into the ratio 66:9:25, no special provision being made for the SS.
While the SS was free therefore to solicit volunteers, it could give them no assurances, even if they met its standards, that they would eventually secure a posting. That would depend upon the Wehrmacht's goodwill and they strictly rationed the SS to no more recruits than would fill out its prescribed divisional strength. The announcement of the raising of its two new divisions won grudging approval from the Wehrmacht for the release of the necessary quota from the manpower pool, but raw lads of eighteen to twenty were of no use to a man in a hurry, like Himmler. He needed trained men immediately if his new division were to take place in a campaign which was expected no later than the upcoming spring.
The solution which he hit upon is an illuminating demonstration of his skill in manipulating administrative machinery, and his readiness to compromise with his conscience. Reluctant to turn away the flood of teenage applicants which a nation wide recruiting campaign had brought in, he formed for each division a replacement cadre which could hold them until they were trained. To fill out the skeletons of his new divisions meanwhile, he decided on wholesale embodiment of formations of the Totenkopfverbande which till this time had been strictly used as camp guards and of the German civil police. The incorporation of the former, who were of course not strictly soldiers at all, was made possible by a loophole in the Fuhrers decree of 1938. These allowed Himmler to call up older men on the outbreak of war to replace the permanent units of concentration camp guards.
These units, in particular Totenkopfverband-Standarten 1, 2, and 3 were drafted into the second of his new divisions (henceforth known as Totenkopf) and were replaced by newly formed units of volunteers. Thus he created a reserve pool for his field divisions, and one over which the Wehrmacht could exercise no control. The formation of his third division was made possible by his decision to suspend the voluntary principle in its case. Thus it was that thousands of constables suddenly found themselves in field grey and faced with a program of training which, for many, was taxing to men of their years. As a result this division, Polizei remained as something of a second class unit for some time.
With Poland conquered and Slovakia subjected, a third solution to the manpower problem, and one which in the long run was to prove the most effective, offered itself to Himmler and to his chief of recruiting, Gottlieb Berger. This was to enlist volunteers from among the Polish and Slovakian Volksdeutsche, those German speaking communities which the Nazis chose to regard as citizens of the Greater Reich and whose existence justified in their view the enlargement of Germany's frontiers to include their homelands. The history of the Volksdeutsche under Nazi rule was to be as unhappy as almost any other people Europe, treated as they were, to be as pawns of Nazi racial policy, but in 1940 the programme of displacement and resettlement which they were to undergo had not yet begun in earnest. their future under German rule looked bright and their young men volunteered for the SS enthusiastically. They were as enthusiastically accepted, for German. Though the Nazi leaders insisted that they were German, the German state did not yet regard them so and had no means therefore to conscript them into the Wehrmacht. The SS was therefore free to recruit as many as it could find without any interference from the army.Their members were still insufficient to provide sizeable contingents but the principle was a promising one.
Taken from ""Waffen SS the asphalt soldiers" by John Keegan
Hope this helps some. I could go on for awhile yet. Also a lot of it also had to do with "Empire building", Himmler viewed himself as some kind of Norse god/soldier/settler. All the big leaders were into it. Goering had his Para Divs and later the Luftwaffe Field Div's. Speer had his own Transportflotte Speer, and Transportkorps Speer, There was the TENO and RAD construction units, all with their own command structure, uniforms, rank insignia etc.
