Command & Conquer: Red Alert 3/Stalingrad

Escort mission
For the first part, you have an MCV and four mechatangu units. The goal is to get your MCV down the river and to the base location without losing the MCV.

Group your mechatangus on one hot key and your MCV on another. Lead down the river with your MCV, with the mechatangus coming behind. Let the MCV draw the fire of the infantry on the shores and then once they are engaged hit them with your mechatangu so your mechatangu don't get damaged. Your MCV can take infantry fire all day without much damage, so don't fret. When you come to the fjord, you need to take your MCV north and use its special move to unpack it near the green arrow. At this point you need to use your mechatangu's special ability to switch them into planes to combat the twinblades that attack. Set up your base and start a power plant, and you'll be pulled away for a mission briefing.

Main mission
Set up two ore factories for the ore deposits next to you, but don't expend much energy to gather the two other unclaimed ore deposits nearby. In this mission all ore is shared equally between the two commanders, so there's no reason to try and beat the other guy to it unless you have nothing else to do.

When you come back, you should have your power plant ready. If you haven't played Rising Sun before, you need to know that all the buildings come out rather quickly as mobile units (called nanocores), and then you move them to their position and set them up using their special move. Setting up the units requires additional time. Build another power plant, dojo, and mechabay. Build three base defender structures, and set them up to defend your base from the north and northwest (don't worry about the northeast).

In this mission on medium difficulty, you'll notice a few harassing infantry, maybe one armored unit, and no air units attacking your base the whole time. So base defense isn't much of a priority. Advance your technology enough to get tsunami tanks, then build attack forces of mechatangu (in air support mode) and tsunami tanks.

Send them to the west to destroy the statue that is closest to you. There are three money crates there. I'm not sure if these funds are shared or not, so you might as well get them.

Next, send a force to the northeast to get three statues up there and about 5 or 6 money crates. You'll get attacked by waves of two and three infantry units at a time, so transform your mechas to infantry mode to defend while your tanks take out the three statues.

Now, there's only the main base and statues around it. You can take this out really quickly with your partner, but instead, prepare for the next phase since at this point the outcome is not in doubt and your partner can handle the base attack solo.

The next part will have a ton of inbound transports for your side that come from both east and west sides of the map, down the river. Soviet units will miraculously appear and attack them, and you have to defend them. This is hard if you don't try to prepare for it beforehand.

So, leave the base and final statues to your partner, and line the river with defenses. Build a ton of defender emplacements -- you can set them up anywhere, not just within a certain distance from your base. So put defender towers all along both sides of the river, then put groups of tsunami tanks and mechatangus (in air mode) all over both shores. When you're all set, make another force to go help your partner destroy the remaining soviet buildings and statues.

Transports coming
When the transports start arriving, they will be attacked by groups of infantry, small groups of armor (including apocalypse tanks) and a few twinblades.

Realize that a single apocalypse tank is a really tough challenge for the units you have available to you. Your mechatangus will not scratch it, and a group of 5 tsunami tanks will (usually) take one out and be left with maybe one wounded survivor.

Keep all of them alive and you'll progress to the next mission.