With Sita's whereabouts confirmed, Rama led the vanara host southward to the very edge of the land, where the ocean barred the way to Lanka. The crossing seemed impossible. Rama, in the older telling, sat in fast and prayer upon the shore for three days, entreating Samudra, the lord of the sea, to grant passage. When the ocean did not answer, Rama at last took up his bow in wrath — and the sea-god rose, abashed, to counsel a solution: let a bridge be built, for the waters would bear it.

The task fell to Nala, the vanara architect, son of the divine craftsman Vishvakarma, who had the gift that whatever he cast upon the water would float. The army laboured for days, uprooting hills and felling great trees, hurling boulders into the sea. The causeway — remembered ever after as Rama Setu or Nala Setu, "the bridge of Rama" or "of Nala" — stretched a hundred yojanas across the deep, and the host crossed over to the demon island.

In the beloved later tradition, especially in devotional retellings, the stones are inscribed with Rama's name and float by the power of that name alone — a tender parable that the Lord's name lifts even what should sink. To this same affectionate stratum belongs the squirrel who carried grains of sand to fill the gaps, whose striped back is said to bear the marks of Rama's grateful fingers; these touches are not in Valmiki's austere Sanskrit but in the warm imagination of the bhakti poets.

On the farther shore the war began. It is worth noting that the conflict is not framed as a simple clash of good against evil. Ravana's own brother Vibhishana, repelled by the injustice of holding Sita, defected to Rama and was welcomed and later promised Lanka's throne — the epic insisting that righteousness, not birth or species, decides allegiance. Embassies were sent; the noble Angada carried Rama's last offer of peace, which Ravana scorned. Then the armies met. The battle of Lanka, narrated in the great Yuddha Kanda, is a vast and grievous thing — heroes fall on both sides, Lakshmana is struck down and revived, and the demon ranks, for all their terror, are slowly broken against the courage of Rama's friends.