Duryodhan had always been ready for war with Paandav, but since his Maamaa Shakuni was with him, he always suggested some kind of cheating. First he planned for Bheem's killing by feeding him Kheer; second time he planned to kill all Paandav along with their mother Kuntee by burning them in Laakshaa Grih fire and third time he planned the cheating by making them lose in dice game. He did not succeed in the first two but he succeeded in defeating them in dice game.
So why Duryodhan was ready to fight? Because he was sure that he would win the war. Why? Because he had such warriors in his army that Paandav could have never defeated his army. Here I would like to count the warriors of his army on which he was counting, and you will find that he was counting right.
Bheeshm Pitaamaha was great warrior. He was educated by Prashuraam Jee himself and had defeated him once. Besides he had the boon of Ichchhaa Mrityu (he could die only whenever he wanted) from his father Shaantanu. He had already taken vow to kill only 10,000 soldiers daily, not the Paandav.
Dronaachaarya was another great warrior. Apart from the warfare training from his father Bharadwaaj, he had obtained many weapons and warfare tricks from Parashuraam Jee too. Besides he himself was the Guru of Kaurav and Paandav.
Ashwatthaamaa was the son of Dronaachaarya. He was also a great warrior and was immortal.
Kripaachaarya was the disciple of his father Sharadwaan and was immortal too. before meeting Dronaachaarya, only Kripaachaarya was training Kaurav and Paandav in warfare education.
Karn was another great warrior. As he was a Kshatriya, he never liked Duryodhan's Maamaa Shakuni's cheap tactics. He was always in favor of war. He was born with Soorya Dev's natural Kavach (armor) and Kundal (earrings) as his lifesavers and good luck. To save his son Arjun, Indra had to take those Kavach and Kundal in alms from him appearing in disguise of a Braahman. Indra was not satisfied with this only, Krishn wasted Indra's Shakti (Power), given by him in exchange of the Kavach and Kundal, on killing Ghatotkach, Bheem's son. Karn was made powerless by his Guru Parashuraam Jee by cursing him that whatever he had learnt from him he would forget when he would need that education very badly; and was cursed by a Braahman that he would be killed when his chariot would stick in the earth and he would not be able to take it out. Poor Karn.
Dushaasan was also very mighty. He had 10,000 elephants power in his body, like Bheem. Duryodhan had a lots of trust and faith in him and he was his right hand. Dushaasan also loved him very much and he was always ready to obey him whether he ordered him for a justified or unjustified work, that is why he misbehaved with his elder sister-in-law Draupadee.
Shalya was another great warrior, that is why Duryodhan cheated him and made him join his side. Besides being a great warrior, Karn himself has told about Shalya, that there was no other Saarathee (charioteer) equaled to Shalya who could stand against Krishn. That is why Karn requested him to be his Saarathee and he served that position for two full days. After that he was appointed the Chief Commander of Kaurav Army , on the last day of the war - the 18th day, and he held the front for half a day.
Duryodhan himself was also a great warrior. He was a Gadaa fighter and he had learnt Gadaa from Balaraam Jee. Although Bheem also learnt Gadaa from Balaraam Jee but he was more skilled than Bheem because then he practiced it for all the 13 years with an iron statue. Krishn Himself has accepted his skills in Gadaa when in the last, on the 18th day, Bheem and Duryodhan were ready to fight. He said to Paandav - "You all five with your combined efforts also cannot defeat Duryodhan." That is why He had to point Bheem to kill him by cheating - by breaking his thigh according to his vow taken at the time of the dice game.
Eklavya, Jaraasandh and Shishupaal
Unfortunately these three were killed before MBH war, but if they had been alive at that time they would surely be fighting from Duryodhan's side and he had some more feathers to his army. Krishn himself has said to Arjun about these three in Drone Parv - "If Jaraasandh and Eklavya had been alive, they would have been terrible..... They jointly could have won the whole world.... They could not have been killed even by Indra himself. Once Jaraasandh hurled his Gadaa at us. Balaraam Jee stopped by his weapon, so it fell on the earth and split it. After losing his Gadaa he was killed by me.... Even Bheem was unable to kill him. He got tired after fighting with for 29 days, then Krishn made a sign at him and that is how he killed him.
Eklavya was weakened by Drone by asking his thumb. Otherwise he was like second Parashuraam. he was capable of shooting day and night and was unable to be won even by Devtaa,
Shishupaal was another mighty king, that is why Jaraasandh wanted Bheeshmak's daughter Rukminee to marry Shishupaal. He was invincible even by Devtaa and Raakshas together."
He had several other major warriors also, including Raakshas, Naag etc who were trying to seek revenge from Bheem and Arjun, that is why they were bent upon to kill Paandav and that is what Duryodhan wanted. Thus there is no doubt that Duryodhan would have surely won the war if Krishn had not killed his major warriors by cheating..... (see Vishnu Cheats)