Definition of "flanck"

The Musketeers being on both flancks, firſt firing let the Ranck ſtand, and fire every Ranck, paſſing through before his leader […]

1684, Richard Elton, The compleat body of the Art Military […] ‎, 2nd edition, page 196

But he was never heard to ſay, that it was I, that gave this Command, who took the Enemies in the flanck, […]

1686, Monſieur de Buſſon, translated by Ferrand Spence, The Hiſtory of the Life and Actions of that Great Captain of His Age the Viſcount of Turenne […] ‎, 2nd edition, page 303

[…] commanded that part of his cavalery which was behind his foot, to charge the King's and the general's regiments in the flanck, just at the time when they were so warmly ingaged at push of pike with his men.

1816, James Stanier Clarke, The Life of James the Second King of England Etc […] ‎, page 14