Kientsch was born on 12 May 1921 in Kißlegg in the district of Wangen im Allgäu, at the time in the Free People's State of Württemberg of the Weimar Republic.

[2] Following flight training,[Note 1] he was transferred to the Ergänzungsstaffel (Training/Supplement Squadron) of Jagdgeschwader 27 (JG 27—27th Fighter Wing) on 27 May 1941.

[2] At the time, the Gruppe was commanded by Hauptmann Erich Gerlitz and equipped with the Messerschmitt Bf 109 F-4.

[5] Kientsch was credited with his first aerial victory on 18 March when he claimed two Curtiss P-40 Warhawk fighters shot down.

Gruppe claimed four aerial victories over near Ain el Gazala and Tobruk for the loss of one Bf 109 shot down by a pilot from the Royal Air Force (RAF) No.

Gruppe lost its leading fighter pilot to date, Oberleutnant Otto Schulz, who was shot down and killed in action.

Gruppe moved to an airfield named Menastir located on the Bay of Sallum and then to Sidi Barrani three days later to support the Axis forces fighting in the Battle of Mersa Matruh.

[15] Two days later, the Gruppe moved to a makeshift airfield named Quotaifiya, located approximately 50 kilometers (31 miles) east of Fukah where they stayed until 30 October.

However, his opponent may have been misidentified as the American born Squadron Leader Robert Louis Mannix, who was shot down and posted as missing in action that day, matched time and location of claim filed by Kientsch.

[18] Here on 27 November, Kientsch claimed his last aerial victory over North Africa when he shot down a Supermarine Spitfire fighter near Ajdabiya.

The pilots then handed over the remaining four serviceable Bf 109s to JG 77 and was then flown on Ju 52 from Tripoli to Sicily and Naples.

The personnel travelled by train to Bari where they received factory new Bf 109 G-4 trop aircraft.

At 12:30, the United States Army Air Forces (USAAF) attacked the Luftwaffe airfield at Trapani with 19 Boeing B-17 Flying Fortress bombers.

Defending against this attack, Kientsch claimed an escorting Lockheed P-38 Lightning fighter shot down near Marettimo.

That day, bombers of the USAAF 17th, 310th, 319th, 320th Bombardment Group targeted Trapani and Borizzo Airfield in Sicily.

Defending against this attack, Kientsch claimed an escorting P-38 and a North American B-25 Mitchell bomber shot down.

There, the Gruppe received new Bf 109 G-6 aircraft and replacement pilots and trained for defense of the Reich missions.

Gruppe flew its first operational combat mission when the USAAF VIII Bomber Command targeted Stuttgart.

Gruppe claimed nine aerial victories, six were later confirmed including two by Kientsch,[29] for the loss of one pilot killed in action.

[28] On 11 January 1944, VIII Bomber Command targeted German aircraft production in central Germany, attacking the cities Halberstadt, Magdeburg, Oschersleben and Braunschweig.

[32][33] On 29 January 1944, Kientsch was killed in action when during aerial combat he crashed his Bf 109 G-6 "Yellow 3" (Werknummer 440 073—factory number) into the ground near Würrich.

[28] According to Obermaier, Kientsch was credited with 53 enemy aircraft shot down, 16 of which in North Africa, 25 in Sicily and 12 in defense of the Reich.