The Japanese felt the Type 4 heavily dominated the P-40, but again each side usually judged in an optimistic light.
Joe, the first JAAF unit equipped with the Type 4 fighter (Ki-84), the 22nd Sentai, deployed to Hankow on August 24, 1944 with 40 aircraft. Over the course of a month, they lost six pilots including the Sentai Leader Maj. Iwahashi, Jyozo. (Only approximately 20 Ki-84 remained to be turned over to the 25th Sentai) In return, the 22nd Sentai claimed 40 aircraft shot down or damaged. Unfortunately, these claims far exceed the actual air-to-air losses of the U.S. 14th AF and Chinese-American Combined Wing (CACW).
In their first action over Yochow on August 28th, the 22nd and the 48th Sentai intercepted 11 bomb-carrying P-40N of the CACW escorted by 13 fighters from the 14th AF. The 22nd Sentai lost one pilot and the 48th Sentai lost two. One Chinese and three US P-40's failed to return.
On the following day, the 22nd Sentai fought P-40N of the 3rd Fighter Group of the CACW on a bombing mission near Heng Yang. One 22nd Sentai pilot was lost as was a Chinese deputy squadron leader. There was also heavy fighting over Yochow when P-40N of the 5th Fighter Group CACW and P-51 from the 23rd FG, 14th AF escorted B-24 on a bombing mission. But the JAAF fighters intercepting that raid was from the 25th Sentai.
A 22nd Sentai pilot was lost Sept. 1st in Central China but the CACW and Chinese Air Force units did not make any claims, (may have been a 14th AF aircraft.)
No air-to-air losses were suffered by Allied units on Sept. 5th and 7th when the 22nd Sentai was in action supporting the capture of Ling-ling.
On Sept. 12th, the 22nd Sentai lost another pilot when they intercepted eight P-40N's from the 5th FG CACW on a bombing mission to Heng Shan. One American pilot was lost and a Chinese pilot crash landed on return to base.
On Sept. 19th, the 22nd Sentai lost another pilot fighting 16 P-40N of the 5th FG CACW on a bombing mission to Hsin-shih. No CACW aircraft were lost. One Chinese pilot claimed a "Hamp" and another claimed one damaged.
On Sept. 21st, the commander of the 22nd Sentai Maj. Iwahashi was lost on a strafing attack on Hsi-an Airfield. Chinese sources indicate that the JAAF ace was hit in the head by ground fire and killed (not by ramming a P-47).
On the same day, a fierce dogfight broke out over Hsin-shih when 15 P-40N of the 5th FG, CACW on a bombing mission was intercepted by JAAF fighters. The 25th Sentai lost two pilots and CACW pilots claimed two "Hamp". Capt. Phil Colman, the only ace from the 5th FG, CACW, made of the claims. He saw the "Hamp" catch fire and crash. One Chinese pilot was killed when his damaged P-40N crashed into a mountain side returning to base.
The 22nd Sentai lost at least 10 Ki-84 during their first deployment to Hankow. Only about 20 out of 40 remained to be handed over to the 25th Sentai.
Even if the 22nd Sentai Ki-84 were responsible for all the Allied aircraft lost in action they participated in (highly unlikely), they still would not have "broken even". Hardly a picture of "dominance".
Most of these actions took place at low altitude while the P-40N's were on bombing missions. At these low altitudes, the single-stage supercharger of the Allison V-1710 engine in P-40N was not at a great disadvantage to the Ha-45-21 engine with two-stage supercharger in the Ki-84. At higher altitudes, the two-stage supercharger of the Ki-84 would see increasing advantage over the single stage supercharger of the P-40N. However, by this time, Japan had begun to face shortages of high octane aviation gasoline which may further erode the advantage with Ki-84.
Another factor to consider is:
The CACW pilots were well trained, experienced and employed sound tactics (e.g. good mutual support with a number of kills scored while shooting JAAF fighter off the tail of friendly fighters).