May I choose a planet to attack in an opposing system where I already have tokens?

Question

Attacking a planet where you already have tokens would ordinarily make no sense, but I saw a player forced to do so recently because they already had tokens on all 4 planets (the 5th had earlier been blown up).

We did not see anything specifically prohibiting this in the rules, and we looked a little online, but could find nothing. So we decided that the player must choose a planet to attack, and if the defending player had no tokens there then the defender would have to defend with zero tokens, as usual. Winning obviously didn't help the player on offense, but the attack had to happen.

Is this the correct interpretation of the rules, or is a redraw of the destiny pile permitted in situations like this?

In this particular scenario, the player who was forced to attack under these unfavorable circumstances likely would have won if not forced to attack a system where gaining a base was impossible.

Answer 1

You played this correctly.

The only rule explicitly stating that the offense gets to change their Destiny card is when they draw their own system. The rule book is also explicit that the defending player must still defend, but with 0 ships (on page 12):

As stated earlier, if a player has no colony on a home planet that he or she is defending, the player defends the planet normally except that his or her ship count is zero.

This section covers your problem. The offense drew a system where the defense had no colonies, so the offense picks a planet and attacks normally. The player whose home system is being attacked still gets to defend, but with 0 ships.