Yuddha Kanda is known as Lanka Kanda, this book describes the war
between the army of Rama and the army of Ravana. Having received
Hanuman's report on Sita, Rama and Lakshmana proceed with their allies
towards the shore of the southern sea. There they are joined by Ravana's
renegade brother Vibhishana. The apes named Nala and Nila construct a
floating bridge (known as Rama Setu) across the sea, using stones that
floated on water because they had a Ram's name written on them. The
princes and their army cross over to Lanka. A lengthy war ensues. During
a battle, Ravana's son Indrajit hurls a powerful weapon at Lakshmana,
who is badly wounded. So, Hanuman assumes a gigantic form and flies from
Lanka to the Himalayas. Upon reaching Mount Sumeru, Hanuman was unable
to identify the herb that could cure Lakshmana and so decided to bring
the entire mountain back to Lanka. Eventually, the war ends when Rama
kills Ravana. Rama then installs Vibhishana on the throne of Lanka. On
meeting Sita, Rama asks her to undergo an Agni Pariksha (test of fire)
to prove her chastity, as he wants to get rid of the rumors surrounding
her purity.