Mariana Islands Campaign

I used Arnold on the carrier, Patton on the heavy tank, MacArthur on a 3X inf Cossack cav, Tassingy on a 3X inf Irish Guards (optional, can use transport instead an place the KV on the heavy tank), Govorov on the heavy arty Katyusha and Cunningham on the 4-hex ship.

Reinforcements: carrier, tank, 3X inf and 3X torpedo bomber.

Smith to head under the southernmost city. The rest are to flank the nearby ship and destroy it on turn 1.
Land your tanks and inf to form a deep beachhead and aim to take the city by turns 2-3. Protect your Katyusha.

Clear out the island. This is a relatively easy task, but expect tight enemy formations and a 3-hex ship at the SE port. Your carrier will be spawned at this port. Send Smith or Tassigny on transport to capture this port and the offshore oil rig.
Your ships are to destroy the NW fleet and provide cover fire for the land forces. The carrier should clear out any existing coastal arty inf.
Note: You should NOT lose any whole units at this point. Every unit matters in GOG3.

After clearing out the enemies, latest by turn 8, the southern island is unlocked.
Move your ships down to protect Arnold. I lost him immediately when I accidentally thrust him into Yamaguchi's waiting fleet.
Along the way, try to stack and heal your troops until they reach full HP and stacks.

If Smith or Tassingy are available earlier during the battle of Saipan, turn them into engineers and build coastal forts on the southern side of the island.
When the other island appears, the enemy will attempt an amphibious assault with naval support. Block this attempt and work with allied ships to take out Ozawa ASAP.

The reinforcement inf can be used as paratroopers to land on the northern tip of the island.
When you have captured the northern port, prepare an amphibious assault and coordinate the attack with the paratrooper drop.

Nagumo is at the SW corner on a carrier. Minimally, the enemy's land fort and coastal fort at the centre of the western coast are needed. It's best if you can build more to fire on him.
Make sure to heal Cunningham so that he can engage Nagumo.
Once the eastern fleet is completely cleared out, any troops on the SE of Saipan can attempted to land along the NE coast of the southern island. The reinforcement carrier can sail into the SE port.

Remember to heal your inf and coordinate your troops to clear out enemy units! Bleed out too much and you'll fail.