Writers have characterized the origin of shanties (or perhaps a "revival" in shanties, as William Main Doerflinger theorized) as belonging to an era immediately following the War of 1812 and up to the American Civil War. This was a time when there was relative peace on the seas and shipping was flourishing. Packet ships carried cargo and passengers on fixed schedules across the globe. Packet ships were larger and yet sailed with fewer crew than vessels of earlier eras, in addition to the fact that they were expected on strict schedules. These requirements called for an efficient and disciplined use of human labor. American vessels, especially, gained reputations for cruelty as officers demanded high results from their crew. The shanties of the 19th century could be characterized as a sort of new "technology" adopted by sailors to adapt to this way of shipboard life.