yadṛcchayā — by its own accord; ca — also; upapannam — arrived at; svarga — of the heavenly planets; dvāram — door; apāvṛtam — wide open; sukhinaḥ — very happy; kṣatriyāḥ — the members of the royal order; pārtha — O son of Pṛthā; labhante — do achieve; yuddham — war; īdṛśam — like this.