The Supply Depot allows you to transfer resources to and from your allies. Upgrading the building will increase the resource help capacity and will lower the trade and President’s taxes.
Reaching level 21 will boost your trade march speed. Reaching level 22 will give you boosts for: trade march speed, gathering march speed, troop load and gold gathering speed.
The number of Trade marches you can send at once is set by the level of your Fort.
The Resource Help Capacity is the maximum amount of resources you can send in a trade march.
The Trade Tax is the amount of resources lost on the road when transferring resources.
The President’s Tax is a revenue the President receives from each Trade March.