@linkler to attack the Soviets in July 39 before they have an opportunity to declare war first Germany will only have one turn to purchase tanks and mechs and place them in range to get to Warsaw/Romania in Jan 39 and then to Moscow in July 39 with the lightning war. There will not be enough units to capture Moscow with that. Germany doesn’t have enough production slots available to put enough down in that first purchase. - remember that the first turn
You are able to purchase blitzing medium tanks is July 38.
Also: you are going to attempt to sign the Molotov pact with the Soviets to buy you that time needed to build up your tanks and mechs (and position them in Warsaw/Romania)