Instead of West Point, McIver joined the private army of the East India Company when he was only 16 years old. He was sent to India in 1858. At that time, the Sepoy Mutiny (Sepoy - native soldiers in the East Indian Company army) raged in India.
In his first battle, McIver was seriously wounded.
In 1860, McIver fought under Giuseppe Garibaldi in Italy, and after that joined the pretender for the Spanish crown, Don Carlos. When the American Civil War broke out, Henry McIver joined the Confederate side.
Although he was only 20 years old at the time he was already an experienced soldier. While fighting for the Confederates, he was under the command of three famous Confederate generals: Jackson, Stewart and Smith.
When the Confederacy capitulated, McIver fled to Mexico, where he joined Emperor Maximilian in fighting Juárez’s rebels.
In Mexico he was captured by Indians, and escaped three months later by swimming across the Rio Grande. He fought at Monterrey, and for his deeds received the title of count. When the Juárez rebellion was successful, Maximilian was executed, and McIver fled to Tampico, where he boarded a ship and left for South America.
In the War of 1877-1878, McIver offered his services to the Serbians, initially being commissioned a colonel of volunteers and later rising to the rank of general and overall cavalry commander of the Serbian contingents.
In 1883, McIver organized a company for British colonization of New Guinea. The project had to be abandoned in 1884 after failing to gain the approval of the Earl of Derby.
McIver died in 1907.