Hanumaan brought the news of Seetaa and after getting news of Seetaa, Raam prepared to invade Lankaa. Raavan got their information at every step since they came across the sea. At that time he said - "It is very difficult to cross the sea. Let them come, our Raakshas will get plenty of food. And they have only monkeys and bears in their army, what do they know about warfare?"  Somebody said - "It was only one Vaanar who burned your whole Lankaa and killed so many mighty Raakshas." But still Raavan was not changing his decision. 

Vibheeshan also advised him last time to return Seetaa to Raam and save Raakshas family and Lankaa, but he insulted him. Vibheeshan went to Raam leaving Raavan. Raam welcomed him and got lots of information about Raavan and his Lankaa. Raavan sent his spies there, they were recognized and beaten. They told Raam's army's account. They also agreed that Raam's army was difficult to win. Raavan got very angry at this and said - "You eat my food and admire my enemy?"

Then Raam and His army crossed the sea. Raavan saw that army from a distance with the help of those spies. Raam sent Angad as a peace messenger to Raavan but Raavan sent him back without any result. Mandodaree tried her best but he said - "You talk with women-like nature. Talk like a wife of a brave mighty warrior."

So the war broke. One by one all were killed - Kumbhkarn, Meghnaad, Raavan's other sons; and in the end Raavan himself too.