Halo Wars: Definitive Edition

This is by far the hardest mission in the game on Legendary!

My strategy for Mission 4: Arcadia City

The overall focus in order of importance:
1. Wipe out the early Covenant attackers, and then race around the city eliminating as many scattered Covenant as you can before the timer reaches around 17:30--when you can finally build a base.
2. Be very generous with the Leader Heal Power! Use it on the Transports as often as possible!
3. Build up a base and spam Hornets as soon as possible--Warthogs are pretty much useless on this level.
4. Protect Transport 1 as long as possible--you need to keep it alive as long as possible, then shift all your defenses to Transport 2. If you lose Transport 1 in the first 10 minutes you might as well restart!
5. Use hornets in run and gun tactics, knocking out Locusts and Wraiths fast.

My general walkthrough steps:
1. As soon as the mission starts, select all units with and target them towards the town hall where citizens are being slaughtered---have Forge run over grunts, and quickly take out all the units there. The hornets and Forge devastate Ghosts.
2. Once that area is clear, try to make a circle around the city, killing any Covenant you find. Make sure to Mass Attack, otherwise you'll lose units. Have Forge run over Covenant as often as he can, and try to keep Forge moving so he's a harder target.
3. Once Transport 3 starts talking, head over there and carefully wipe out all the Covenant near it--try to keep Forge from blowing up!
4. After T3 blows up, possibly send one Hornet down to your future base site which is pretty much where you started on the map, and have Forge and the other Hornets all go guard Transport 1.
5. Start building your base, and rush to get Hornets--build 2 supply pads, 2 Reactors, an Airpad, more Supply pads, a Field Armory, and upgrade things...
6. As well as building Hornets! Make sure to keep Hornets coming out, and use them to reinforce the defenses at Transport 1.
7. If you see any Locust or Wraiths coming, mass attack them, then pull back to the defenses at Transport 1.
8. Use your Leader Heal Power as often as you can to heal Transport 1 primarily, and then Transport 2 if T1 is good.
9. Build at least one Turret on your base on the top left corner, and equip it with an anti-infantry upgrade.
10. Using your Hornets, protecting the Spartans, and using your Heal power, you should be able to balance things to keep T1 alive as long as possible. The Covenant will build a mega-turret that will take out T1 in a few shots, but there usually isn't enough time left for them to attack T2 also--
11. If/When T1 gets blown up, shift ALL defenses over to T2, although guarding the Spartans is a good idea as well. Protect it, heal it, shoot down Banshees ASAP, etc.
12. If it's gone well, you'll win!
13. If not... you'll lose. It took me 4 tries on Legendary this time around to finally succeed. What got me a success was using my Heal Power as often as possible, as well as keeping the Spartans in the fight.. not to mention knocking out the Locust and Wraiths ASAP.

This was one tough mission. A fun challenge in an otherwise not to hard game!