Infinity War - "We are in the end game now".

I'm not sure if this has been discussed here yet, but based on a lot of comments I see, there are many people that might not know of this particular angle -

A chess game is broken down into three parts:

The Opening: A chess opening is the group of initial moves of a game (the "opening moves"). Recognized sequences of opening moves are referred to as openings.The fundamental strategic aims of most openings are similar: placing the pieces (particularly bishops and knights) on useful squares where they will have an optimal impact on the game.

The Middle Game: The middlegame is the part of the game which starts after the opening. There is no clear line between the opening and the middlegame, but typically the middlegame will start when most pieces have been developed. Because the opening theory has ended, players have to form plans based on the features of the position, and at the same time take into account the tactical possibilities of the position. The middlegame is the phase in which most combinations occur. Combinations are a series of tactical moves executed to achieve some gain. Middlegame combinations are often connected with an attack against the opponent's king.

The End Game: The endgame (also end game or ending) is the stage of the game when there are few pieces left on the board. It is presumed that you will lose a number of your pieces during the opening and middle game stages of the game, and so you seek to keep and position certain remaining pieces for a final "End game" attack sequence.

In the context of Infinity War - Dr Strange knew that some prices would have to be sacrificed in order to be positioned properly against Thanos during the final sequence of play, in order to be ultimately successful - hence why he states "We are in the end game now".