Theory:

    Ranji waited. The other boy made a strange, hissing sound. They stared each other in the eye for almost a minute. Then the Warrior slapped Ranji across the face with all the force he could muster. Ranji staggered, feeling quite dizzy. There were thick red finger marks on his cheek.
 
    “There you are!” exclaimed his assailant. “Will you be off now?”

    For answer, Ranji swung his arm up and pushed a hard, bony fist into the other’s face.

    And then they were at each other’s throats, swaying on the rock, tumbling on to the sand, rolling over and over, their legs and arms locked in a desperate, violent struggle. Gasping and cursing, clawing and slapping, they rolled into the shallows of the pool.
Explanation:
 
Ranji then waited for the other boy to start fighting. On the other hand, the Warrior made a weird sound, perhaps to signal the start of the fight or to terrify Ranji to run away from there. After that, they both stared at each other for about a minute. The Warrior started the fight by slapping Ranji in the face with all of his might. Feeling unsteady, Ranji almost lost his balance and felt a sensation that he was spinning around. As a result of the slap, thick red finger marks formed on Ranji’s cheeks.
 
Later the Warrior remarked, “There you are”. It implies that after getting a slap from the Warrior, Ranji felt unsteady, and so he came up with a statement that this was only the capacity of Ranji. He portrayed him as a weak one and asked him to leave his place. Within a quick moment, Ranji raised his arm and gave a punch in the Warrior's face with his strong, bony fist.
 
fight_2.jpg
Ranji gave a punch in the boy's face
 
The next moment both of the boys began to fight with each other. The narrator later explained the fight between the two boys. Initially, the two boys fought each other by moving back and forth on the rock. It suggests that they were competing to prove who was the best. They then fell and rolled over each other on the sand. Later, their arms and legs were locked against each other in a desperate and brutal wrestle.
 
On the other hand, Ranji and the Warrior used many offensive words while rolling about in the shallow pool. In addition, they had trouble while breathing. Meanwhile, they took a rapid, deep breath through their mouth while battling. It implies that they could not breathe normally due to the constant fighting; thus, they would gasp in between the fights. At last, both of them kept fighting and panting and rolled into the shallows of the pool.
 
Meanings of the difficult words:
 
S.No
Words
Meanings
1
StrangeUnusual or surprising; difficult to understand or explain
2
SlapHit or strike with the palm of the hand or a flat object
3
AssailantA person who attacks his enemy
4
Stagger Walk or move unsteadily, as if about to fall
5
Dizzy Having or involving a sensation of spinning around and losing one's balance
6
SwayMoving slowly or rhythmically backwards and forwards or from side to side
7
GaspCatch one's breath with an open mouth, owing to pain or astonishment
8
CurseUtter offensive words in anger or annoyance
9
Tumble Fall suddenly, clumsily, or headlong
10
DesperateFeeling or showing a hopeless sense that a situation is so bad as to be impossible to deal with
11
ClawScratch or tear something with the claws or the fingernails
Reference:
National Council of Educational Research and Training (2008). It so happened. The Fight- Ruskin Bond (pp. 45-54). Published at the Publication Division by the Secretary, National Council of Educational Research and Training, Sri Aurobindo Marg, New Delhi.