When does a Showdown begin?

Question

Accepted Answer

A showdown begins when control of a battlefield becomes contested or when one or more units move to an empty battlefield.

According to **Rule 340**:
*   **340.1:** If control of a battlefield is contested between two players, a showdown is opened as the first step of combat.
*   **340.2:** If a battlefield is uncontrolled (empty) and becomes contested by a unit moving into it, a showdown is opened during the cleanup at the end of the action that caused the battlefield to become contested.

**Important nuances regarding when a showdown does NOT begin:**
*   Moving a unit to a battlefield you already control does not trigger a showdown (it is simply a reinforcement).
*   A showdown cannot start while a chain is currently resolving; it will stage and start at the first open state after the chain resolves.
*   Only one showdown can exist at a time. If multiple showdowns are staged, they must resolve one after another.