Drona as Commander of the Kuru Army
After the defeat of the grandsire Bhishma, the command of the Kuru army was bestowed upon Dronacharya by Duryodhana. Drona was a great warrior and he was an expert in the use of all the weapons. He had the blessing of defeating his opponents single handedly. Under his command, the huge army of the Kauravas regained their courage and strength which was degraded to some extent after the defeat of Bhishma. Dronacharya killed thousands of soldiers and generals from the side of the Pandavas. He had however made a promise to kidnap the eldest Pandava, Yudhisthir, in order to let the Kauravas win the battle. Thus, he worked out a battle-plan and it was called Chakravyuh. The knowledge of that form of battle was only known to Arjuna and therefore Arjuna was carried away by some Kuru generals far away from the Pandavas by tempting him for a solo fight. While Arjunawas away, the Pandavas, unknown about the Chakravyuh, were helpless and at that time Arjuna's son Abhimanyu came forward and told that he had some idea about that form of the battle and thus took leave from Yudhisthir to fight against the Kauravas.
While Arjuna was away fighting with two Kuru generals, the four Pandavas were unaware of the plot constructed in the battle by Dronacharya. Dronacharya implemented the Chakravyuh, a form of warfare, in order to arrest Yudhisthir. By that time Abhimanyu came to the eldest Pandava and told him that he was able to break the defense formed by the Kuru general and thus took leave from Yudhisthir and went away. Abhimanyu was a great warrior and he fought very bravely and was able to break the defense of the Kuru army and was able to get to the center of the force. There he was surrounded by seven great warriors of the Kurus which also included Duryodhana, Dushasana, Karna and Jayadratha, King of Sindhu. Abhimanyu fought very bravely with the seven warriors and was successful in giving them severe wounds. However, at last, the seven warriors, forgetting all the rules and regulations of warfare, surrounded him from all sides and killed him mercilessly in the battle field.
Jayadratha was the husband of the only sister of Duryodhana and he was also that person who insulted Draupadi when the Pandavas were in exile in the forest. In the great battle at Kurukshetra, Jayadratha fought in the side of Duryodhana and he was the main person who was responsible for slaying Abhimanyu. After the death of Abhimanyu, atmosphere in the camp of the Pandavas became utterly melancholic and while Arjuna returned from the battle, he came to know of his son's death. He heard how his son fought very bravely and how he was slain mercilessly by the seven warriors with the head being Jayadratha. Thus, Arjuna promised to kill Jayadratha the next day in the battle and if he would not be able to kill him before the Sun sets, then he vowed to sacrifice himself in fire. The next day, with the rising Sun, the battle began and as per the instructions of Duryodhana, Jayadratha was protected by all the Kurus. However, Arjuna succeeded to get Jayadratha away from the defense of the Kauravas and killed him.
Ghatotkacha was the son of Bhima and Hidimbi. While Ghatotkacha learned about the great battle at Kurukshetra, he took leave from his mother in order to take part in the battle from the side of the Pandavas. While Ghatotkacha reached the Pandava came, the Pandavas were delighted to find a fierce warrior in their side. With the son of Bhima in the battle, the vast Kaurava armies were unable to proceed further due severe obstructions from Ghatotkacha who used his magical power in the warfare. He grew very tall and used to kill the soldiers by hundreds by crushing them under his feet. Seeing the helpless condition of their army, Duryodhana persuaded his fried Karna to kill the son of Bhima. Karma fought with Ghatotkacha very bravely and was killed by Karna with the aid of a celestial weapon which he had preserved to kill Arjuna.
The most vital part of the Drona Parva is however the way in which Dronacharya was killed in the great battle at Kurukshetra. Dronacharya was blessed to defeat any foe single-handedly and which he also did by slaying thousands and thousands of Pandava soldiers and generals in the battle. He had all the celestial weapons in his possession and thus was considered to be invincible. The Pandavas, after removing Bhishma from the battle, were then in deep trouble in order to find a way in which Drona could be defeated. The Pandavas came to know that as long as Ashvatthaman, the son of Drona, lived it would never be possible to conquer Drona, since the love and hope for his son were sufficient to keep him filled with courage and energy. Bhima, therefore, for the defeat of Drona, selected an elephant named Ashvatthaman and slew it with his own hands, and then threw himself before the Kuru army and shouted that he had killed Ashvatthaman. Hearing the news of his son's death, Drona at once came to Yudhisthir to ask him the truth and Yudhisthir also consented to what was told by Bhima but he also told slowly that the elephant named Ashvatthaman was killed which was not heard by Bhishma. Thus, Bhishma gave up all his weapons and sat in meditation on the ground and that time, Dhrishtadyumna, the commander of the Pandava army, chopped the head of Drona with his sword.
The Drona Parva, thus, ends with the death of a number of great warriors including Abhimanyu, Ghatotkacha and finally the death of Dronacharya. This seventh parva of the great epic of Mahabharata, thus, narrates very minutely and clearly all the incidents relating to Dronacharya becoming the general of the Kuru army after the defeat of Bhishma and his subsequent death in the battle in the hands of Dhrishtadyumna, the son of Drupada.