The fighting spirit, it is to be understood. The fighting spirit is there in the Supreme Personality of Godhead, and it is exhibited at a certain period just to teach us . . . (indistinct) . . . when fighting should be taken. Fighting is not very good thing, but if there is necessity . . . just like in the Battlefield of Kurukṣetra. The Battlefield of Kurukṣetra was organized by two rival parties. One party was pious; another party was impious. So Kṛṣṇa took side of Arjuna, and he was victorious. That is the history of Kurukṣetra fight.
So the Lord wanted to exhibit His fighting spirit. And who will fight with Him? Therefore two of His devotees were resigned that they should go in the material world and fight with the Supreme Personality of Godhead. Because in the Vaikuṇṭha world there is no question of fighting. There is no enmity. Everyone accepts the Supreme Personality of Godhead as the protector, as the master, as the Lord, and they serve faithfully. So there is no question of fighting.
In the material world everyone wants to be the lord, everyone wants to be God, so therefore there is fight. The fighting here takes place because everyone wants to lord it over the material nature, so there is difference of interest. I want to be lord, you want to be lord: now there must be fight. But in the Vaikuṇṭha world there is one Lord and all others servitor. Therefore there is peace.
So fighting was not possible in the Vaikuṇṭha world—therefore these two doorkeepers were sent to the material world by the plan of the Supreme Lord so that they could fight as Hiraṇyakaśipu and Hiraṇyākṣa with the Lord. That is stated in the Śrīmad-Bhāgavatam.