Two words: UCS. Japan.
You might need to use more than two. Let's start with the game you're playing and work from there.
I was killed by a travelling mountain that apparently has guns. That was a really good run too, I had about 4000 echos worth of stuff between my boat and my home.
Earth 2150 has three separate campaigns, and the one I was playing was the UCS (United Civilised States). Japan is notorious for a lot of players because of how difficult it is. You're given units that have the health integrity of rice paper, and you've probably ran out of research funds back at HQ if you're not careful, so you'll be stuck at that level if you're not careful.
The enemy, on the other hand, surrounds you and generally have superior weaponry, which is either lasers (overheats your unit and then blows it up) or electro-cannons (knocks your units internal systems offline then blows it up). It'll generally take you a long whileon the UCS campaign scraping by with grenades and rockets.
Basically, you're outfunded, outgunned, surrounded, and outteched.
But, if you like microing... You will love this.
It took a lot of manoeuvring and savescumming, but I survived the first onslaught. I have a large group of Gargoyles (light fighter craft) that are knocking out power plants and supply lines. It's working well, I guess?
I still hate this mission.