On this day, 13 May 1943 Fw. Karl Willius would have his best day as a Jagdwaffe pilot, claiming no less than four VVS aircraft in two separate missions. The first three was all Pe-2 bombers downed in the early morning hours, all within a space of 15 minuts, the last one was a MiG-3 shot down at 14:02. Thereby he increased his score from 23 to 27 abschusse. Willius would add another four VVS fighters, all LaGG-3s before I./JG 26 left the Eastern Front and returned to the channel on 6 June 1943.

On the channel front "Charly" Willius would chalk up another 19 US and Brittish aircraft, 17 of them was later confirmed. His last claim was filed on 8 April 1944 when he shot down a B-24 Liberator from the 44 BG in a head-on attack. His target was seen dropped out of formation in flames and became his 50th, and last, victory. The Fw 190s from JG 26 then climbed back into the sun following their attack. As they were reforming, USAAF P-47 bounced them. Willius' Fw 190 A-8 (W.Nr. 170 009) "Black 5" was hit by 1/Lt. Alton B. Snyder, from the 361 FG and Willius machine was seen to spin into the ground and explode. His body was not recovered until 1967, buried in his aircraft in a Dutch polder. Willius was awarded a posthumous Ritterkreuz on 9 June and promotion to the rank of Oberleutnant.