What does the active player do immediately after the beginning of combat step begins in a multiplayer game?

In a multiplayer game of Magic: The Gathering, when the beginning of combat step starts, the first action the active player takes is selecting an opponent to be the defending player. This is a fundamental part of the combat process and establishes who is involved in the combat for that turn.

Choosing a defending player is critical because it determines who will be attacked and how the combat interactions will unfold based on the creatures declared as attackers and blockers. This choice sets the stage for the rest of the combat phase, including the declaration of attackers and blockers that follows in the next step.

Following this, the active player will progress to declaring which creatures are attacking and subsequently, if combat continues, the defending player will declare blockers. Assigning damage and drawing a card do not occur at this point in the beginning of combat step; they happen later in the combat phase with damage assignment and during the draw phase respectively.