I'm not talking about Marseillais chess (which is similar, but rules are added to reduce the advantage of the white), which is sometimes also called "balanced double-move chess".
In a Double-Move chess both players move two times instead of once. There is no check, capture the king to win.
Is the advantage of white sufficient? I.e. is it feasible to prove that white can always force a win?
Was a question like this examined in the past? I'm looking for references on any related work.
For example, if we were talking about Triple-Move chess (both players move three times instead of once, there is no check, capture the king to win), then white always wins on the "second move" by sacrificing the queen. That is, white makes their "first move" by:
pushing e pawn, queen to h5, queen to f7, and black is lost!
To see why black is lost, observe the
f1 bishop. It can capture the king on the next move either by
b5, d7, e8 or by
c4, f7, e8 (the white queen must be captured). If black captures the queen with anything but the king (i.e. spends two moves on the knight), then black does not have enough moves to defend both lines of attack from the bishop. Otherwise, if black captures with the king, then there are again two lines of attack from the
f1 bishop and black again does not have enough moves to defend both. Black king gets captured on the "second move" in every scenario.
If we reduce the variant to Double-Move chess, is the advantage for white still significant enough such that we can possibly find the (least?) number of moves in which the white can force a win (capture black king), or is this variant as hard as solving the ordinary chess?
Edit: I'm aware that "If there was a perfect play from both sides, but each player was allowed to do 2 moves every time, would white win?" was asked before, but there it is not clear if the OP refers to the (balanced) Marseillais chess, or not. - Also, the answer there isn't useful as it simply states "White would probably win. However, this is not certain..." without further clarifications. (I.e. they appear to claim that it is as hard as ordinary chess, but this is not obvious.)