Born in Denver, Colorado to Alfred E. and Hersa A. Lea, his father served with the 3rd Colorado Cavalry during the . His mother died before his third birthday, 13 August 1879. Alfred is listed in the Jackson County, Missouri 1850 census, Washington Township, with the entire family being born in Tenessee.
His grandfather, Dr. Pleasant John Graves Lea , is the namesake for Lee's Summit, Missouri, although the name became spelled with an "e" instead of "a" because a stone culvert next to the Missouri Pacific Railroad station was set this way.
Homer was born healthy, but after suffering a drop to a hearthstone as a baby, he became a , standing only with a weight under . He attended Los Angeles High School and even accompanied friends on camping trips in the San Bernardino Mountains, in spite of his physical hindrances. Lea aspired to be a great soldier and somehow managed to get an appointment to , though he was soon dismissed for health reasons. He was later admitted to Stanford University, where in addition to military history and politics, he became enamored with China and .
At 23, with the Boxer Rebellion underway in China, Lea decided to travel to the Far East and offer his services to Kang Youwei, a former prime minister of China who was attempting to restore power to the confined Guangxu Emperor. Lea convinced Kang to make him a lieutenant general and give him command of a small volunteer force. Lea's first command was not very successful as Kang's power and support was rapidly destroyed, but he did make it to Beijing in time to ride through the city with the international force that liberated it from the Boxers. Lea offered pursuit of the retreating , but his rag-tag soldiers were no match for the Imperial forces and he was repulsed. Without any support after Kang's fall, Lea fled to Hong Kong and then Japan, where he met Sun Yat-sen.
Sun was intrigued by the diminutive foreigner and saw his natural flair and western background could be useful in building support for the republican movement. He therefore dispatched Lea along with Prince Ch'i-ch'ao to the United States to raise funds. Lea returned to China in 1904 at the head of the Second Army Division, but this military campaign was unsuccessful and he was forced to return to the United States for health reasons.
Once in the U.S., Homer Lea was instrumental in training the , using American soldiers as instructors. Lea was also an author of two works on geopolitics: ''The Valor of Ignorance'' predicted the rise of Japanese militarist aggression and a in the , while ''The Day of the Saxon'', commissioned by Field Marshal Lord , predicted the rise of a greater based on national supremacy and ethnic purity. Neither of these books sold particularly well in America, but ''The Valor of Ignorance'' sold 84,000 copies in Japan and impressed both General Adna Chaffee and General Douglas MacArthur, who tried unsuccessfully to make it compulsory reading at West Point. The books both contained a ring of truth about future events, but entrenched in America were not about to have their views challenged by a young, unknown upstart, and he was effectively ignored. His books remain little known today, as his theories were not particularly revolutionary; other geopoliticians could also see the same forces converging, but the public did not want to hear about it. Lea also planned to write a third book called ''The Swarming of the Slav'' predicting a Russian move to dominate Europe, but he died before he could complete it.
When Sun Yat-sen succeeded in making China a republic in 1911-1912, he made Lea a full general and his chief of staff. A stroke several months later, however, forced him to give up these positions and retire to the United States, where he died at age 35, in .
* 1908: ''The Vermilion Pencil: A Romance of China''. - New York: McClure. -
::Reprinted 2003. - Stirling: Read Around Asia. - ISBN 9780954545000
* 1909: ''The Valour of Ignorance''. - London, New York: Harper and Brothers. -
::Reprinted 1942. - ISBN 1931541663
* 1912: ''The Day of the Saxon''. - Harper and Brothers. -
::Reprinted 1942. ISBN 1932512020
*Anschel, Eugene, . - ''Homer Lea, Sun Yat-Sen, and the Chinese Revolution''. - Praeger Pubs. ISBN 0030000637
*Alexander, Tom, . - "The Amazing Prophecies of 'General' Homer Lea". - ''Smithsonian''. - p.102.