Mezue ahịrịokwu na-esonụ: N'elekere ise nke ụtụtụ n'abalị isii nke ọnwa Eprel, ndị agha Luftwaffe Messerschmitt Bf 109E 20 wakporo ọdụ ụgbọ elu Sorlince, na-ebibi ụgbọ elu niile nke 2nd Air Reconnaissance Group nke ejikọtara na 5th Army. Ka otu awa gachara, ndị Luftwaffe wakporo ebe ụgbọelu Niš, merụọ ụgbọelu anọ nke 610th Eskadrila. N'oge mwakpo a, German na-efe efe ace na onye isi nke &lt;a href="Lehrgeschwader%202%23I.%28Jagd%29/LG%202"&gt;I. (Jagd) /LG 2&lt;/a&gt; Herbert Ihlefeld bụ onye obere egbe gbara ọkụ na-amanye ya ka ọ daa na mberede n'akụkụ obodo Donji Dušnik, mgbe nke ahụ gasịrị, ndị agha Yugoslavia tụrụ ya mkpọrọ.
Igbu Belgrade n'ụtụtụ nke Eprel 6 butere mbibi nke nkwukọrịta n'etiti ndị isi ndị agha nke ise na ndị isi ndị agha Yugoslav.