Hetman's army on the march. Probably the infantry-Serdyuk (Part of painting of unknown Polish artists of the late 17th century.)

Serdyuk, or serdiuk pl. serdiuky (serdenyata, convivial serdyuk's (willing infantry) regiments, Ukrainian: сердюк) were mercenary infantry units kept by the Hetman's Zaporizhzhya Army from the second half of the 17th century through the first quarter of the 18th century and formed the Hetman's guard. Serdyuk recruited mainly from the Ukrainian population and the Kozaks of Cossack Hetmanate and Zaporizhian Sich. The average Serdyuk regiment consisted of 400-500 soldiers. They served at the border and inside the country, and guarded the Hetman's residence. By decree of the Russian Tsar on July 14, 1726, the convivial serdyuk's units were disbanded.

Sources

• Бутич І. Л. Сердюки // Енциклопедія історії України : у 10 т. / редкол.: В. А. Смолій (голова) та ін. ; Інститут історії України НАН України. — К. : Наук. думка, 2012. — Т. 9 : Прил — С. — С. 541. — ISBN 978-966-00-1290-5.(in Ukrainian)