Successfully complete the game with any Wei officer to unlock Sima Yi.

Play the Battle Of Wu Territory with the Allied forces on the hard difficulty setting.
When Sun Quan gets ambushed in the west fort, kill him before Zhou Tai meets up with him.
Then, defeat Zhou Tai.

Successfully complete the game with Xiahou Dun and Zhang Liao to unlock Xiahou Yuan.
Alternately, play half the character's Musou mode.

Successfully complete the game with Cao Pi to unlock Cao Ren.

Play the Invasion Of Nan Zhong with the Wu forces on the hard difficulty setting. Rescue
Sun Quan after he is ambushed, then defeat all officers.

Successfully complete the game with any three Wu officers to unlock Huang Gai.

Successfully complete the game with Sun Ce, Sun Quan, and Sun Shang Xiang to unlock Sun
Jian. Alternately, successfully complete the game with Zhou Tai to unlock Sun Jian
quickly.

Certain characters have Jump Charge attacks (A + Y) that send them high in the air (for
example, Jiang Wei and Yue Ying). Use this move on a watchtower and the top of the tower
will fall off and the bottom will stay standing for a few seconds.

Successfully complete the game with Ling Tong to unlock Gan Ning.

Play the Battle Of Mt. Ding Jun with the Wei forces on the hard difficulty setting. Kill
Huang Zhong, Zhao Yun, Wei Yan, and Guan Ping before Cao Cao gets there.

Play the Battle of Mt. Ding Jun with the Shu forces on the hard difficulty setting. Defeat
Xiahou Yuan and Zhang He before Cao Cao arrives. The weapon report will show up when Cao
Cao appears.

Play the Battle of Chang Shan with Yuan Shao's forces. After defeating Lui Bei, Guan Yu,
or Zhang Fei, defeat the remaining two generals in less than one minute to get the Red
Hare Harness.

Defeat Meng Huo each time that he appears during the Nanman Campaign to unlock Meng Huo.
Alternately, successfully complete the game with Zhuge Liang and Lu Xun in Musou mode.