Synonyms:

yadrcchaya–by its own accord; ca–also; upapannam–arrived at; svarga–heavenly planet; dvaram–door; apavrtam–wide open; sukhinah–very happy; ksatriyah–the members of the royal order; partha–O son of Prtha; labhante–do achieve; yuddham–war; idrsam–like this.

Translation:

O Partha, happy are the ksatriyas to whom such fighting opportunities come unsought, opening for them the doors of the heavenly planets.