nirīkṣya - after observing; pṛtanām - his own soldiers; devaḥ - the demigod Indra; paraiḥ - by the enemies; abhyarditām - put into great difficulties or oppressed; raṇe - in the battlefield; udayacchat - took up; ripum - the enemies; hantum - to kill; vajram - the thunderbolt; vajra-dharaḥ - the carrier of the thunderbolt; ruṣā - in great anger.

When Indra, who is known as Vajra-dhara, the carrier of the thunderbolt, saw his own soldiers so oppressed by the enemies on the battlefield, he became very angry. Thus he took up his thunderbolt to kill the enemies.