Arjuna went to Duryodhana in the camp. Duryodhana received him well: "Come on, brother. What do you want?" He thought that "We are fighting. Arjuna has come to beg the kingdom without fighting." So they were so liberal. He said, "Yes, come in. If you want the kingdom without fighting, I am prepared." But a Kṣatriya will never beg, "Give me, sir, without . . ." No. If they can own by fighting, then they will claim. This is Kṣatriya spirit.
So he said that, "No, I have not come to beg the kingdom. We shall fight, go on fighting. But I want those five arrows you have kept." Oh, immediately he delivered. Although he was very cautious that these five arrows may not be missing, but promise is promise. Immediately he delivered. So Bhīṣma understood later on that the five arrows were taken by Arjuna by trick. So still, he promised that, "Even without those five weapons, today I shall kill Arjuna. Unless Kṛṣṇa gives His special protection to Arjuna, there is no escape. Either Kṛṣṇa has to break His promise, otherwise His friend will be killed."
So Kṛṣṇa, when He joined Arjuna, He said that He would not fight: "I can help you simply by becoming your charioteer, but I cannot fight." Because the purpose was that Arjuna was to gain the fight. But if Kṛṣṇa would fight, people would say that Kṛṣṇa won the fight, not Arjuna; that he avoided fighting. It was sure. Kṛṣṇa fights or not fights, because He was on the side of Arjuna, it was sure that he would gain the battle. That is explained in the Bhagavad-gītā. Yatra yogeśvaro hariḥ (BG 18.78). Where there is Kṛṣṇa, the victory is assured.