Colonel James Hsu is a field-grade officer in the New California Republic Army in 2281, commanding NCR operations in the Mojave Desert from his headquarters at Camp McCarran. He is level-headed and soft-spoken, maintaining a calm demeanor despite recognizing the many problems plaguing his command. If asked how he can be so calm when so much is going wrong, Hsu matter-of-factly replies that it is a necessary part of being a leader and dealing with things that are beyond one's control. Hsu knows how to use force to solve problems, but prefers diplomacy whenever possible, as opposed to his counterpart, the hawkish Colonel Cassandra Moore or the NCR Army's chief, the gung-ho General Lee Oliver.
Hsu displays considerable understanding of the political and military situation in the Mojave, recognizing the difficulties the NCR faces. He cares a great deal about his soldiers and rangers put under his command and works steadily to better their situation. His combination of high competence and dedication with a great deal of modesty has made him well-liked by his men, drawing the ire of General Oliver, who may see him as an up-and-coming rival. Craig Boone remarks that if it weren't for General Oliver's interference, Hsu would have already been a general a long time ago.
In dialogue originally intended to be heard after the second Battle of Hoover Dam but still available in-game while the battle is going on, Colonel Cassandra Moore says that upon learning of the NCR's success in the Mojave, her superiors first turned to Hsu since he was in command of operations in the area, but he denied having anything to do with the victory. As a result of his modesty, Hsu gets passed over for promotion and Moore is promoted to brigadier general instead.