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[laiocfar]

You can upgrade units inside secured cities*, it takes one turn and the prestige for the new equipment. Anyway in first scenario your tanks are only usefull to kill the polish tank unit(the Pz35tn can handle it) and to move fast and surround the polish town in the east for attack enemy artillery(none of your avaible tanks is up to the task without artillery and infantry support). Watch out for the AT in the objetive at north, it can wipe your green crews in that cheesemade tanks.

*The city is secured when it passed 2/3 turns since takeover and when there inst any unit next to it. Only secured city/airfields can upgrade or build new units.