Stealth Units Not Showing When Attacked

In my latest HWW game, me (Romania) attacked Tehran (belonging to British India) with a stack of 3 level 3 Light Tanks. There were 2 units in the city: a level 2 Artillery and a level 1 SPAA. I figured I would be able to eliminate the stack and conquer the city easily. However, when the stacks first engaged in combat, my stack took WAY more damage than the arty/spaa is capable of giving. However when I examined the enemy stack it still showed only the arty and spaa. No stealth units, nothing. About 30 minutes later, I logged back in to check on the battle, and upon the next iteration reset I could (finally) see the stealth units: 2 level 1 Commandos and 1 level 2 Tank Destroyer. Had I seen these units upon first attacking the city, I would have sent air support to attack the stack. I thought that stealth units were supposed to be visible to the other player when they are engaged in direct combat. Either fix the bug, or reword the manual so as not to confuse people like me. Thank you!