He served in the Mexican-American War and the Civil War. Commanding the vastly outnumbered Union forces at the Battle of Monocacy, he was defeated on the battlefield, but delayed the Confederates by a day, allowing Union reinforcements to arrive at Washington, D.C. before the Confederates. At 71 years of age, he attempted to enlist for the Spanish-American War.
At different times in his life he was a Whig, a Free Soil man, a Democrat, and a Republican. He was involved in a Free Soil newspaper for a time. He was the appointed governor of the New Mexico Territory, in which position he had dealings with a notorious criminal known as Billy the Kid. He then served as minister (ambassador) to the Ottoman Empire (i.e. Turkey) for several years.
Frankly, Lew Wallace had a long and varied career. When the country was at war, he served it in a military capacity. When it was at peace, a variety of private pursuits and public service occupied him for almost eighty years. He was an outstanding American with an interesting life that seems vaguely improbable - until one considers even larger-than-life figures such as Theodore Roosevelt and Winston Churchill. In comparison, Lew Wallace almost seems prosaic - but only almost.