Just a clarification. If at the start of combat at the first planet Player 1 has Units committed there and Player 2 has 0. Can player 2 still take actions during the battle at the first planet? Say to Fire an Ork Kannon or Ambush a Unit to the Planet?

Yes.

Player 1 does not win the combat until they try to take a shot (i.e., exhaust a unit to attack) against an empty field.

But before Player 1 gets a chance to take that shot, both players get the chance to trigger actions. So Player 2 does get the chance to bring units in before Player 1 wins.

and about the ambush units: let's say I don't have initiative, but there's an action window during combat in which my opponent doesn't do anything. Can I deploy, say, my eager recruit and attack immediately with him?

That's been bugging me a lot... cause action windows are kind of "in the air" if you get my drift. It's not as black and white as in M:TG. Still, I love the game though.

You can ambush in any action window, but you can still only attack when it's your turn to attack. Ambush doesn't give you a free swing unless you time it right.

Action windows open and close precisely at the times specified in the gameflow chart defined in the RRG pp 20-22. Which in turn precisely defines when units with Ambush may be deployed. An action window can only close once both players have passed successively. This means the answer to your question is that It's irrelevant who has initiative, you can deploy your eager recruit in the action window prior to your combat turn and attack with him.once that action window has closed. Note that this isn't quite "immediate" though - the action window only closes after successive passes, so other actions may be done during the action window before it closes and your combat turn commences.

You can ambush in any action window, but you can still only attack when it's your turn to attack. Ambush doesn't give you a free swing unless you time it right.

I see, I saw a video on youtube where the guy attacks with a Sicarus Chosen, then immediately attacks again with an eager recruit to finish the enemy unit before it had time to react. I take it he didn't play by the rules?

I see, I saw a video on youtube where the guy attacks with a Sicarus Chosen, then immediately attacks again with an eager recruit to finish the enemy unit before it had time to react. I take it he didn't play by the rules?

If there were no other ready units for them to attack with this is fine, but otherwise no - ambushing in a unit does not give you a free attempt to swing with them for two attacks in a row. Ambushing before the other person has passed their combat turn simply means they can either kill the ambushing unit before it attacks with one of their ready units, or ditto with an ambush unit of their own.

That said it is perfectly legitimate to deploy in the window before your attack and then swing with the ambush unit - and really an unexpected attack seemingly out of nowhere is kind of what an ambush is about.

I see, I saw a video on youtube where the guy attacks with a Sicarus Chosen, then immediately attacks again with an eager recruit to finish the enemy unit before it had time to react. I take it he didn't play by the rules?

If there were no other ready units for them to attack with this is fine, but otherwise no - ambushing in a unit does not give you a free attempt to swing with them for two attacks in a row. Ambushing before the other person has passed their combat turn simply means they can either kill the ambushing unit before it attacks with one of their ready units, or ditto with an ambush unit of their own.

That said it is perfectly legitimate to deploy in the window before your attack and then swing with the ambush unit - and really an unexpected attack seemingly out of nowhere is kind of what an ambush is about.

good point! I'll have to watch the video again to see if other units were readied.

I see, I saw a video on youtube where the guy attacks with a Sicarus Chosen, then immediately attacks again with an eager recruit to finish the enemy unit before it had time to react. I take it he didn't play by the rules?

If there were no other ready units for them to attack with this is fine, but otherwise no - ambushing in a unit does not give you a free attempt to swing with them for two attacks in a row. Ambushing before the other person has passed their combat turn simply means they can either kill the ambushing unit before it attacks with one of their ready units, or ditto with an ambush unit of their own.

That said it is perfectly legitimate to deploy in the window before your attack and then swing with the ambush unit - and really an unexpected attack seemingly out of nowhere is kind of what an ambush is about.

good point! I'll have to watch the video again to see if other units were readied.

Don't hold on to much on videos. Check the rulesbook with the phases and the Action windows, it will become much more clearer for both you and your opponent when you continuously check what widows there are.

In many cases the Eager Cadet will be played in the Action window that will accur before the beginning of a new battle. After playing it your opponent also has the option to react with something that can be played as an Action or play an Ambush card, if this is not the case both playes would continue the initial battle in which case often only the Eager Cadet can strike.