unconquerableness

From unconquerable +‎ -ness.

unconquerableness (uncountable)

1. The quality or state of being unconquerable.
   • 1625, Peter Heylyn, “Of the World: And First of Europe. The Grecian Iles.”, in Μικρόκοσμος [Mikrókosmos]. A Little Description of the Great World. […], revised edition, Oxford, Oxfordshire: […] Iohn Litchfield and William Turner, and are to be sold by W. Turner and T. Huggins, →OCLC, page 424:

     VVhen all the Perſians ſoothed the King in the vnconquerableneſſe of his forces, Artabanus told him, that he feared no enemies but the Sea and the Earth; the one yeelding no ſafe harbour for ſuch a Navie; the other not yeelding ſufficient ſuſtenance for ſo multitudinous an Armie.

• William Dwight Whitney, Benjamin E[li] Smith, editors (1911), “unconquerableness”, in The Century Dictionary […], New York, N.Y.: The Century Co., →OCLC.