Definition of "unflinching"

Can an honest, upright and Christian man, go into these conflicts, and with unflinching firmness stand up for all that is good, and oppose all that is evil, in whatever party it may be found, without a measure of moral courage such as few can command?

1837, Catharine E. Beecher, An Essay on Slavery and Abolitionism, page 126

[…] I abandoned myself implicitly to the guidance of my wife, and entered with an unflinching heart into the intricacies of her studies.

1839 November, Edgar A[llan] Poe, “Morella”, in Tales of the Grotesque and Arabesque, volume I, Philadelphia, Pa.: Lea and Blanchard, published 1840, page 10

If only she would wake and close her mouth, mentally prayed the outwardly unflinching girl. Later the doctor came, and sheltered by his presence the sick woman's husband stood in the doorway.

1907, Barbara Baynton, edited by Sally Krimmer and Alan Lawson, Human Toll (Portable Australian Authors: Barbara Baynton), St Lucia: University of Queensland Press, published 1980, page 208

For all the glories of the Ferguson end-game, Manchester City’s rise and Arsenal’s unflinching desire to finish in the top four and occasionally win the FA Cup, this is now Chelsea’s mini-era.

2017 May 13, Barney Ronay, “Antonio Conte’s brilliance has turned Chelsea’s pop-up team into champions”, in the Guardian‎