Attack

An attack sends ships from one of your planets or moons to somebody else's planet or moon, to break whatever is guarding it and take the resources sitting on it. If anything is home when your fleet arrives there is a battle. Win it and your surviving ships load up with plunder and fly back on their own.

You cannot capture a planet by attacking it. There is no conquest in SFC2. All you can take away is resources and the debris the battle leaves behind. A planet only ever changes hands when its owner is pruned for going inactive.

Sending an attack

There are three ways to start one, and they all end up at the same form.

From the Fleets page

Open Fleets and pick Attack in the Mission row of the Fleet Dispatch panel, then type the target coordinates into the three Destination boxes (galaxy, system, slot).

As soon as the coordinates are filled in, the ship list loads underneath. Enter how many of each ship you want to send, check the Summary, pick a speed and hit Launch Attack.

Two things about that Summary. The Duration shown is one way, so double it if you want to know when the fleet is home again. The Hydrogen shown is the whole fuel bill and it comes out of the launching planet the moment you click the button.

There is no Cargo box on an attack. Attacks cannot carry resources out. The cargo space on your ships is only used on the way back, for plunder.

From the Galaxy page

Find the target on the Galaxy page and click the lightning bolt in the Actions column. The same form opens in a popup with the target already filled in. The eye next to it sends a spy probe, which is what you should be clicking first.

From a report

Espionage reports, battle reports and harvest reports all carry action buttons at the bottom. Attack reopens the dispatch form pointed at the same planet, and Simulate drops the whole report into the Calculator so you can test the fight before you pay for it.

Speed

Speed runs from 100% down to 5% in steps of 5. Slower means a longer flight and a smaller fuel bill. It also means the defender has more time to see you coming and clear the planet, so most attacks go out at 100%.

Attacking a moon

Every slot can hold a planet and a moon. To aim at the moon instead of the planet, type the slot as a number followed by m, so 9m rather than 9. From the Galaxy page just click the icon on the moon's own row.

Who you can attack

To launch at all you need at least one ship that can move, a free fleet slot (you get one plus one per level of A.I. Tech) and enough hydrogen on the launching planet.

After that, plenty of things can put a target out of reach. The Galaxy page prints a letter next to a player's name when one of them applies:

Letter	What it means
n	Newbie protection, or the two of you are too far apart in size
N	Too strong for you to attack
v	On vacation, immune to attacks, spying and missiles
V	On vacation but idle too long, so the protection has lapsed and they can be hit
d	Protected by diplomacy mode
P	PVE Mode is active, so no player can attack them
i	Inactive for 7 days or more
I	Inactive for 21 days or more

The size rule behind n and N is newbie protection, and it works off resources spent points (RSP):

Under 750 RSP you cannot attack anybody and nobody can attack you.
Once you are both over 750, the smaller player's RSP has to be at least a fifth of the larger player's.
Once the smaller of the two is over 25,000 RSP the ratio stops mattering and anyone can hit anyone.
An inactive defender loses all of it. Nothing on that list protects a player who has been gone 7 days.

A few more blocks that are on your end rather than theirs:

You cannot attack your own planets. Use Transport or Deploy for that.
If you have PVE Mode running you cannot attack any player, only NPCs. Cancel it in the Store first.
Diplomacy mode blocks your outgoing attacks as well as incoming ones.
A planet that you paid to move cannot attack for 24 hours afterwards.
A Hephaestus cannot launch or be attacked while it is in transit.
Suspended accounts cannot launch attacks or spy.

What happens when the fleet lands

The fight runs for at most six rounds. How the shooting itself works is on the Combat page. Once it is over:

Destroyed ships leave a debris field worth 30% of what they cost to build. Recyclers collect it, and either side can go get it. Destroyed defenses leave nothing at all.
70% of the defenses and solar satellites you blow up rebuild themselves for free the instant the battle ends. Expect to shoot most of the same wall again next time.
If the defender has nothing left standing you plunder. That is up to half of the ore, crystal and hydrogen on the planet, or 55% if your alliance is at war with theirs. What you actually carry home is capped by the cargo space of your surviving ships, and a Resource Den keeps part of the stock out of reach entirely. Probes and the Hephaestus carry nothing.
A big enough battle can form a moon in the defender's slot. The chance is the total debris divided by 15,000,000, capped at 20%, and only planets that do not already have a moon can gain one.
Your survivors turn around and fly home with the loot. Both sides get a battle report in Messages.

The Ship Activity panel on Overview and Fleets shows the attack going out and, below it, the projected return leg, so you always know when the fleet is back.

Calling a fleet back

While the attack is still in the air the row carries a Withdraw button. Withdraw turns that fleet around wherever it is. The trip back takes as long as it has already been flying, and never longer than a full flight. A withdrawn fleet never lands, so it does not use up a bashing slot and it does not fight.

Bashing

You can land six attacks on the same planet in any 24 hours. The seventh is refused. Going past that is bashing, and the game simply will not let you do it unless one of the exceptions applies.

The count is per attacking player, per target planet, on a rolling 24 hour window measured from when each attack launched.
Attacks already in the air count against the limit.
If your entire fleet is wiped out, that attack does not count. You get the slot back.
A fleet you withdrew does not count either.
NPC targets are exempt. Farm them as much as you like.
Two alliances that are formally at war are exempt from the limit against each other.
Spying is never blocked by the attack limit. Probe away.

What the defender sees

An incoming attack appears in the target's Ship Activity panel with a red countdown as soon as you launch. How much they can see depends on their Espionage Tech:

Level 0 or 1: only the countdown and where it is coming from.
Level 2: how many ships are inbound.
Level 4: which ship types are inbound.
Level 8: the exact count of each type.

If you are on the receiving end, read What to do When Under Attack and Fleet Saving.

Group attacks

Up to seven fleets can hit the same planet in one battle. Launch the attack yourself, then open Formation on the Ship Activity row to see who is coming and to invite alliance mates and buddies. Your own colonies can join too.

Joining fleets have to be able to show up near the leader's arrival time. The group will hold and wait for a slower fleet, but only up to 30% of the original flight time. Anything slower than that is refused. See Group Attack, and Group Defend for the other side of it.

NPC encounters

The green rows on the Galaxy page are NPC fleets and colonies. You attack them exactly the same way, and they are the main source of easy resources and debris in SFC2. They ignore newbie protection and they do not count towards the bashing limit, so they are also the safest place to test a fleet build. See Non Player Characters.

Work out the fight first

An attack is only cheap if you win it. The Calculator page runs the real battle engine against whatever fleet and defenses you type in, and the Simulate button on an espionage report fills the whole thing in for you. It also reports your losses and the debris, which is how you work out whether the raid actually pays.

The calculator is still in beta, so for anything expensive it is worth cross-checking against Battle Mentat, the third-party tool the game itself points at.