Analysis of information sources in references of the Wikipedia article "Yaya (military)" in English language version.
Ala-ed-deen first embodied a corps called Yaya, or Piade. They were all infantry, and were raised and recruited from the body of the Ottoman population.
The Yaya corps with light armor and problematic combat value was no match against heavily armored Balkan infantry in
Ottoman-Balkan Yaya, early 15th century: Many Ottoman infantrymen were of Christian origin and this seems to have been reflected in their equipment.[permanent dead link]
yayabashi (T. yayaba§i): commanders of foot soldiers.
Since the infantrymen (yaya or piyade) received regular pay, the Ottoman state may be said to have acquired a standing army at this early date.