Wiktionary
unconquerableness
n. The state or quality of being unconquerable.
Usage examples of "unconquerableness".
A denounces B's raiders as pirates and so forth, bombards B's capital, and sets off to hunt down B's airships, while B, in a state of passionate emotion and heroic unconquerableness, sets to work amidst his ruins, making fresh airships and explosives for the benefit of A.