It's really very simple:
1. Your trade page will tell you how much of a particular item you use each month. as far as ammunition, fuel and other consumables that varies with the number of active units.
2. When you set up a military unit of any kind, not only do you have to have the minimum defaults of those particular items but strategic stock remaining for the supply units to draw from.
3. You have to have supply units to restock whatever the equipment uses in a month. If you do not have enough strategic stock to replace whatever is used the unit will dismantle and the equipment moved to deactivated.
4. If you do not have enough supply units to get to all your military units eventually, they will disband due to lack of supplies no matter what your strategic stock levels are. How long it takes in this case I have no idea but if it's taking longer than a game day to replenish all your units at least once (esp.
Thank you so much for this!