The Gītā opens with Dhṛtarāṣṭra asking Sañjaya what happened on the field. It is the only verse he speaks. Every verse after it is the answer to his question.
Going deeper
The first verse of the Gītā is a question from a blind king. In 1.1 Dhṛtarāṣṭra asks Sañjaya what his people and the Pāṇḍavas did when they gathered on the holy field of Kurukṣetra, eager for battle. It is the only verse he speaks. 1.2 is the start of the answer, and the speaker changes: Sañjaya reports that King Duryodhana, seeing the Pāṇḍava army in battle array, approached his teacher Droṇa and spoke. From there the book is Sañjaya's reply, carrying the dialogue between Kṛṣṇa and Arjuna to the king who asked. Notice how the question is put: my people and the Pāṇḍavas. The king's first words already divide the field in two. The opening is in chapter 1, and what the Gītā says about dharma follows the idea the book opens on.