tasmat tvam uttistha yaso labhasva
jitva satrun bhunksva rajyam samrddham
mayaivaite nihatah purvam eva
nimitta-matram bhava savya-sacin

"Therefore get up. Prepare to fight and win glory. Conquer your enemies and enjoy a flourishing kingdom. They are already put to death by My arrangement, and you, O Savyasaci, can be but an instrument in the fight."

Savya-sacin = Arjuna, capable of shooting arrows by the left hand also. Tasmat = therefore, tvam = you [Arjuna], uttishta = get up, yaso = fame, labhasva = acquire, jitva = by winning, satrun = enemies, samruddham = full of prosperity, rajyam = kingdom, bhunksva = enjoy. The Lord tells Arjuna to therefore, get ready and fight his enemies to win them and acquire fame and enjoy the ever flourishing Kingdom. Purvam eva = long ago, maya eva = by Myself [Sri Krishna], ete = all thses [kings and warriors], nihata = were killed or destroyed, nimitta - matram = only a tool, bhava = you [Arjuna] are. 'Therefore' means, the Lord has already decided on the fate of these kings and warriors, and Arjuna has to understand this. The Lord by His will power, decides on everything be it creation or destruction. His will power is also to use Arjuna as a tool to kill them. Therefore, Arjuna has to get up and fight only. Arjuna who had dropped his bow Gandeepa, has to now get ready and take the bow and fight. Arjuna by now would have understood Who the Lord was and what His determination was. Arjuna should now fight so that others do not ridicule him as a coward, but praise him as a hero. He will also enjoy Royal life. He acquires fame and enjoyment. By telling that the fate of these kings had alraedy been decided, it is implied that Arjuna would be beating a dead snake [செத்த பாம்பை அடிப்பது!]. It clearly implies that Arjuna is needed to kill them as the Lord had already decided. He had decided long back when Draupati was humiliated. Just for Arjuna to get name and fame, the Lord had allowed them to live this long, else He could have finished them off then and there itself! Thus the sin of killing them would not be on Arjuna. Nor it would affect the Lord. The past karma of these people would be responsible for their destruction. Arjuna need have no fears - of getting defeated as the Lord has already decided on his victory, of affected by sin, as he is not killing but decided by the Lord, of any adharma as Arjuna is going to be only a tool in this war game. Arjuna has to just dedicate his great skills to the Lord. That is all.