MBH War (Mahaabhaarat War) or Kurukshetra war took place between Kaurav and Paandav. Kaurav mens Dhritraashtra's sons and Paandav means Paandu's son. This war continued for 18 days. In this war only 10 people remained alive from both sides from 18 Akshauhinee army - 7 people from Paandav's side and 3 people from Kaurav's side, all others were dead. Those 10 people were 5 Paandav, Yuyutsu (Dhritraashtra's son from his Vaishya wife) and Saatyaki from Paandav's side and Kripaachaarya, Kritvarmaa and Ashwatthaamaa from Kaurav's side.

How much is 1 Akshauhinee army? -
An army has four wings - Charioteers, elephant riders, infantry (who walk on foot) and cavalry (who fight on horses). One Akshauhinee army contains 21,870 Rath (chariots), 21,870 elephants, 109,350 infantry (soldiers on foot), and 65,600 cavalry (horse riders). This makes up one Akshauhinee army. Paandav had 7 Akshauhinee army and Kaurav had 11 Akshauhinee army. Kaurav army included Shree Krishn's one Akshauhinee Naaraayanee army also.

Who Were With Kaurav and Paandav? -
Kaurav had - Bheeshm, Drone, Kripaa, Ashwatthaamaa, Karn, Shakuni, Shalya (Maadree's brother), Jayadrath (Dushalaa's husband), Kritvarmaa (Krishn's relative), Somdatt, Bhoorishravaa etc with them + 11 Akshauhinee army

Paandav had - Drupad, Dhrishtdyumn, Shikhandee, Draupadee's five sons, Abhimanyu, Saatyaki (Arjun's friend), Ghatotkach (Bheem's son), with them + 7 Akshauhinee army.

Bheeshm -
Bheeshm was the pillar of this war as he had the boon of Ichchhaa Mrityu. Nobody could kill him. He was the Chief Commander for 10 days, then was Drone for 5 days, then Karn for 2 days and lastly was Shalya for half a day. Bheeshm was killed by Shikhandee as he did not fight with women and Shikhandee was the incarnation of a woman, so Bheeshm saw a woman in him and did not counter him.

He had his own conditions of War before he fought from Duryodhan's side. He would not kill Paandav. He would kill 10,000 soldiers daily. He would not counter attack any woman. Till he will be Chief Commander of the army, Karn will never be seen anywhere in the battle ground. When he heard that Krishn would not take up any weapon, he took a vow that he would force him to take up the weapon. He did that not only once, but twice during his 10 days time.

Snce he had the boon of Ichchhaa mrityu, he could not have been killed, that is why Paandav had to go to ask him "how to win Kaurav army as till he was alive and fighting, they could not have won war". Then he told the way that since I do not counter attack on women, you may bring Shikhandee in front of me and I will not counter attack him. So the 10th day Shikhandee was brought in front of him and he killed Bheeshm.

Drone -
For the next 5 days Drone was the Chief Commander. He was also a kind of invincible. He also troubled Paandav's army so much that Paandav had to think some way to kill him. He was the one who planned for Chakra Vyooh which took Abhimanyu's life. Krishn suggested them the way to tell lie to kill him that if you would announce "Ashawatthaamaa died", he would die himself. The main problem was who was going to convince him, and for this Yudhishthir was chosen because he always spoke truth. The same thing happened, when Bheem announced "Ashwatthaamaa died", Drone confirmed with Yudhishthir and he confirmed it in a low voice. After that he just sat down and left his body with Yog. Dhrishtdyumn shot arrows at him but at that time he was not alive.

Karn -
Karn was the Chief Commander for the next 2 days. It is a pity that Paandav did not have to think about any trick to kill him. He was carrying two Shaap with him to be killed, otherwise also his Kavach and Kundal were already taken by Arjun's father Indra and his Power had also been used on Ghatotkach managed by Krishn indirectly. He had nothing to save himself from Arjun.

Shalya and Ashwatthaamaa -
Shalya's commandership is not very memorable, but Ashwatthaamaa created a lot of havoc after his father was killed by a lie. As he heard that Paandav killed his father by announcing a false statement about his death, he filled with rage and he did which he never did throughout the war. He killed Draupadee's five sons, Dhrishtdyumn and destroyed the whole Paandav camp while they were sleeping (of course, since they were sleeping at another place, they got saved). This made Arjun very angry and when he followed Ashwatthaamaa, he used Brahmaastra with half knowledge and directed towards Uttaraa to destroy Paandav Vansh. But luckily Krishn saved it.

From Paandav's Side -
Shikhandee, Arjun, Bheem, Dhrishtdyumn -
Because of Shikhandee and Arjun, Bheeshm fell;
Bheem killed Dhritraashtra's all 100 sons;
Dhrishtdyumn became the cause of death of Dronaachaarya;
Nakul killed his Maamaa Shalya:  and
Sahadev killed Kaurav's Maamaa Shakuni.

Kripaachaarya and Ashwatthaamaa were immortal.