Zhang Liang was an aristocrat from the Kingdom of Han (not the same han as the dynasty Han) before Qin Shihuang united China. After the falling of his home country, he tried to assassinate Qin Shihuang but failed. After escaping for many years, he came under the leadership of Liu Bang. Zhang Liang was known for his wise strategies that Liu Bang used many times. He was one of the most important tacticians for Liu Bang.
Above picture courtsey of China.9c9c.com
Xiang Yu was a huge man with enviable abilities. After the revolt of Chen Sheng, he started another revolt with his father. BC 207, during the battle of Julu, he defeated the Qin General Zhang Han and thus fame arose rapidly. All of a sudden, he became the leader of all of the revolting armies. Later, when he fought Liu Bang for the ultimate winner, because of lack of food of soliders, he committed suicide at the river of Wu after losing to Liu Bang.
Fan Zeng is the tactician for Xiang Yu. He tried to persuade Xiang Yu many times to assassinate Liu Bang but Xiang Yu never listened to him. After Xiang Yu's refusal to take his advise and fell in the trap set by Liu Bang, he left indignantly and died of illness on the way.
Xiang Bo was Xiang Yu's uncle as well as Zhang Liang's good friend. After Zhang Liang's repeting pleas to help Liu Bang to have a good name in front of Xiang Yu, Xiang Bo protected Liu Bang whenever he could, especially at feasts.