Even though Stellar Age is a real-time game, battles have a round based system which determines its outcome.
First and foremost, keep in mind that this is not an everlasting system which can see adjustments in the future, so each mechanic works for a specific patch. Even though this system has not changed much since it’s beginnings, do consider that someday it might.

Battles are resolved in rounds. Who has priority in each round alternates on every round, so, first round is for the attacker, second for the defense, third for the attacker, and so forth until one or the other is destroyed.
One important thing that needs to be taken into account is that, no matter whose turn it is (attacker or defender), hits are exchanged. This means that on any round, the attacking fleet deals damage to the defense, and defense deals damage to the attacker, then the round is resolved and losses for each are calculated.

When a fleet attacks another fleet the procedure is as follows:
1) Smallest attacking ship’s turn (smallest by volume, being Light Fighter smallest and Titan largest). Each ship will choose which enemy ship type to hit, this is what we will call “Targeting”. Target is selected following a priority:
а) Smallest ship against which your ship has bonus; if none,
b) Smallest ship against which your ship has no weakness; if none,
c) Smallest ship against which your ship has weakness.
Once determined, our ships will damage the target, and the target will damage our ships (this is called counter-attack). Destroyed ships are accounted for and the round is over. If ships on both sides still stand we move to the next round.
2) Smallest defending ship’s turn. Ships will select their target (the same way as explained above) and exchange hits with it. Damage is calculated and destroyed ships accounted for. If ships on both sides still stand we move to the next round.
3) Second smallest attacking ship’s turn (if only one ship type, it’s turn repeats).Ships will select their target and exchange hits with it. Damage is calculated and destroyed ships accounted for. If ships on both sides still stand we move to the next round.
4) Second smallest defense ship’s turn, and so forth.

This proceeds until either the attacking or defending fleet is destroyed (or in very rare cases, both) and whoever remains standing is granted the victory.

This battle scheme is used for attacking players’ wrecks/fields, and regular pirates. When attacking other players’ planets there is a slight difference in most common occasions: Defense Towers.
If there are towers on defense, these fight before engaging with the orbiting fleet.