According to the Combat Chronology here:
https://media.defense.gov/2010/May/2...100525-035.pdf
The first 8th Airforce attack against targets in Germany occurred on January 27, 1943.
1/27/43 Eighth AF
53 HBs make first Eighth AF attack on Germany, bombing naval base, U-boat construction works,
power plant, and docks at Wilhelmshaven. 2 other HBs bomb submarine base at Emden.
The first 8th AF attack of the war was done by A-20s on airfields in the occupied Netherlands on July 4, 1942.
7/4/42 Eighth AF
First AAF air operation over W Europe. 15th Bomb Sq, flying 6 American-built Bostons belonging to RAF, join RAF low-level attack on 4 A/Fs in the Netherlands. Aircraft flown by Capt Charles C Kegelman, sq CO, is severely damaged, but Kegelman succeeds in bringing it back to base at Swanton Morley. VIII AF Comp Cmd is activated in US. Second B-17 arrives in UK via N Atlantic ferry route.