I think (not 100% sure), units can't jump up the upgrade queue, so you have to upgrade to the next upgrade first, before you can get the 2nd upgrade. Upgrading the tank units in india takes like forever. Don't plan with them before '43.
In generel its very important to have a look at your replacement pool as allies, as you don't produce troops but get replacements. Allowing too many troops to take replacement will let you end with loads of weak units. For example, check out how many troops/equippment the australian troops are missing at the beginning of the game and have a look at the replacement rate of these...
Bazan you make a good point. Now that you can purchase back virtually any destroyed unit the temptation is to do so. However, the replacement rate for British and Australian squads is so low that you just will not be able to fill them all back up. After 43 you get only 30 Australian squads a month. That is about enough to support about four Australian divisions if they are in heavy fighting. Even with 90 squads per month of Indian units, I have not been able to rebuild many lost Indian units and I am coming up to 1945. American units are not a problem though.
However, you cannot upgrade Allied units until the specific date allowed. They cannot be advanced.
Be careful about your Commonwealth tank units. Don't upgrade them all at once. You will still need the plentiful grant and lee tanks well into 1945.
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