Learn German: Den Atem angehalten, wartet er auf den Gegner. - Breath held, he waits for the opponent.

This is the Absolute Accusative. German uses a standalone accusative noun, often paired with a participle like angehalten, to describe an accompanying physical state or posture. It functions similarly to saying "with his breath held," but without needing a preposition like mit.

Does the phrase Den Atem angehalten count as the first position for word order?

Yes. The entire absolute phrase occupies position 1 in the sentence. That is why the conjugated verb wartet takes position 2, and the subject er is pushed to position 3.

The English translation implies "his breath", so why doesn't the German sentence use the possessive seinen Atem?

In German, when referring to body parts, clothing, or physical states (like breath) that clearly belong to the subject doing the action, you typically use the definite article (den) rather than a possessive pronoun. It sounds much more natural to native speakers.

Why does the preposition auf take the accusative (den Gegner) instead of the dative here?

While auf is a two-way preposition that can take the dative for locations, here it is part of a fixed verb-preposition combination. The verb warten (to wait) always requires auf + accusative to express who or what you are waiting for.