The intensity of aggression and emotions of warriors can only be felt by them when they lose their fellow warriors.
Take a look at this video that is thrilling enough to give you goose bumps:
This video shows the soldiers of 2/1 RNZIR Battalion of the New Zealand Army performing their Unit Haka, strongly acknowledging the lives and feats of their fallen comrades as they come onto the Unit's parade ground.
Haka is used by M?ori (native people of New Zealand) for an innumerable number of reasons; to challenge or express defiance or contempt, to display approval or appreciation, to support or to discourage, to recognize feats and achievements, to greet, to parting, as an expression of pride, happiness or sorrow. There is almost no inappropriate occasion for Haka; it is an outward display of inner thoughts and emotions.
It is also an emotive farewell for they will leave via the Waharoa (the carved entrance way) for the very last time.