I've spent the last hour looking for this game, both on my computer and in the interwebs, so now I come here to ask you good people. I will try to describe it.
First thing I should say is that this is/was a freeware indie game that had previous iterations that were much simpler, but the basic game mechics (especilly combat and destruction) were the same.
There are two teams (orange and blue?) and both start with one city, and there can be a total of 4/6 cities on a map. Other than these two cities the whole map is water, so your options for combat are limited to turrets on the cities, boats on the water, and planes in the air. There are a couple different kinds of each boats and planes. For boats I think there was a cargo boat, gun boat, and a missle boat which functioned as artillery. For planes there was a cargo plane, fighter, and bomber. I think some of those vehicles, and some weapons for those vehicles had to be bought with the money in the game. Both cargo vehicles were for trading between cities, which was a good way to make moneis to buy vehicles and upgrades for bases.
The objective was to destroy all of the enemy bases, there were capital buildings that were built on the cities to take them over, they kept cities under your controll, amnd placing them on neutral cities slowly turned them to your side. Destroying them ment you slowly lost control untill the enemy was allowed to place their own building to try and take the city. Ther were other things you could build on cities too, mines (raw resources), and factories (to turn those into $), turrets, and some other buildings that I forget.
The destruction and combat physics and mechanics were really cool, there were kinetic and explosive weapons. The kinetic weapons were the standard for turrets and gunboats and they fired a sticky cannonball. To buildings it did nothing but stick to the wall, but for boats and planes it could take off wings and the cockpit (for an insta kill), if it didn't break it off the ball would atleast stick and mess with steering and slow you down. The other option was explosive, basicly an insta-kill against most vehicles unless you're lucky. But the main use was buildings, the explosives (cannon rounds, rockets, bombs) would take chunks out of buildings and all the bits would fall into the water. For buildins that actually had purposes other than getting in the way there would be a green glowy center that you had to expose. Once it was exposed the idea was to hit that again with an asplosive and then the whole building would be destroyed in a spectacular explosion with all the bits flying out to land in the water.
Oh yeah, one last thing was the day/night cycle, the whole time you're playing the sun is making it's way across the sky, untill you get to night time, once it hits night time it gets so dark that no one can see, and you can't spawn. People already spawned are still alive, but they can't see anything not currently being illuminated by explosions, boats are forced to either stop or try to continue on their course and hope they don't ram into a wall, or stray too close to enemy islands (AI controlled defense turrets can still shoot just fine). Planes are basiclly fucked because you have no point of reference and eventually you'll crash, hit the edge of the map, or get to close to an enemy base. But while it's dark two things still happen, you still gain resoures at the same rate as day, and you can spend them on upgrades, or research (which goes at the same rate too). Basiclly it gives everyone a quick break to regroup and take stock of the situation.
Well that was a longer description than I thought it would be, hopefully someone recognizes what I'm talking about.