What is Rikki-tikki's great war in "Rikki-tikki-tavi"?

Rikki’s great war was the war against the cobras.

Rikki-tikki’s war was against the pair of cobras, Nag and Nagaina.  As a mongoose, it was his job to get rid of the snakes in the yard, as every good house-mongoose does.

This is the story of the great war that Rikki-tikki-tavi fought single-handed, through the bath-rooms of the big bungalow in Segowlee cantonment. Darzee, the tailor-bird, helped him, and Chuchundra, the musk-rat, who never comes...

Rikki’s great war was the war against the cobras.

Rikki-tikki’s war was against the pair of cobras, Nag and Nagaina.  As a mongoose, it was his job to get rid of the snakes in the yard, as every good house-mongoose does.

This is the story of the great war that Rikki-tikki-tavi fought single-handed, through the bath-rooms of the big bungalow in Segowlee cantonment. Darzee, the tailor-bird, helped him, and Chuchundra, the musk-rat, who never comes out into the middle of the floor, but always creeps round by the wall, gave him advice; but Rikki-tikki did the real fighting.

Chuchundra helped him by telling him to listen for the snakes.  Darzee helped him by distracting the snakes and serving as a decoy, and by warning Rikki off.  However, Rikki was the only one who was able to kill the snakes.

Rikki washed into the garden and found himself in the care of a British family staying in the Indian bungalow.  He wanted to stay because the house was interesting, the people fed him, and it is a mongoose’s duty to watch out for people.

Chuchundra is not much help. He is too afraid to do anything.  He tells Rikki he should have talked to Chua, the rat, instead.  However, in talking to him Rikki hears a snake and knows that it is Nag or Nagaina. 

Darzee turned out to be very useful. He was a smart bird, and warned Rikki when Nag was there.

“Behind you! Look behind you!'' sang Darzee.

Rikki-tikki knew better than to waste time in staring. He jumped up in the air as high as he could go, and just under him whizzed by the head of Nagaina, Nag's wicked wife. 

Darzee’s wife also pretended to have a broken wing to distract Nagaina so that Rikki could go kill all of her eggs.  Rikki had two reasons for doing this. He wanted to eliminate the other cobras, and he wanted to have leverage to use against Nagaina.

Rikki manages to kill both cobras and the little snake, Karait.  Since he kills all of the cobra babies too, the people are safe in the garden.  If another snake comes, Rikki will get that one too.