The Cannes mission gives the primary commander spies and Tanya. The secondary commander gets a full army.
For the first few minutes you may want to use Tanya to assist in attacking or defending to the north. Some combat will occur whether you want it or not.
On the map there is a small island all the way to the east. Use the spies to disable the power plants that are floating in the water around the island. Then use Tanya to remove the tesla coils. This will give the primary commander access to several bombers which will be virtually unchallenged. The primary commander will continue to receive income but have no way to spend it except on bombers anyway.
Next objective is to free the diplomats. This can be done by brute force or by removing the Russian forces first.
There are two ways to approach the Russian base. Use bombers to assault the tesla coils to the south of the Russian base or free the diplomats and walk along the northern edge of the map to get into the Russian base.
There are four dreadnaughts out in the sea off of the Russian base continually bombing just west of the Russian base. Tanya can handle the dreadnaughts, the subs are the problem. Using land based units or Tanya can kill the subs. Using the “f” key will activate Tanya’s time belt and set her back five seconds to her previous health and location, this only works if she is alive.
The alternate commander may want to take a soviet dock with an engineer they aren’t well defended. This will give them access to bullfrogs. The northern base can be handled entirely by the co-commander.
For the main objective use Tanya and some spies to clear out the island in the middle. The bombers will take down the power plants and therefore deactivate the tesla coils allowing Tanya full access. Once Tanya is on the island she will remove the infantry and clear the path for the spies. Finally use Tanya to enter the port authority and destroy all the Russian dreadnaughts still in the water. DO NOT DESTROY THE BUILDINGS IN QUESTION ON THE CENTER ISLANDS.