According to the Pirates Log:

Then came the long-dreaded mission – an attack on the heavily-defended city of Yawata. Crews had been sweating out the “Big Y” since early B-29 days when the XX Bomber Command bombed it from China. Yawata, the fourth most important industrial center of Japan, contained the largest steel works in the Empire.

Of the 245 20th Air Force planes on the mission, the Sixth contributed twenty-seven over the primary target. Enemy opposition was aggressive from fighters with some thirty attacks made against the Group’s formations. Two fighters were destroyed; two credited as probably destroyed. One of the Group’s planes, piloted by Lt Jack A. Henshaw, was badly damaged by machine-gun fire from the fighters and was forced to proceed to Okinawa for landing. Lt Henshaw received the Silver Star for his gallantry in action. Heavy flak was also encountered, but cloud conditions made it inaccurate and only three Sixth planes were damaged. Later photos show 21 per cent more of the city destroyed.

[Pirate’s Log, pp. 53-54]

According to Joe Whitney (Radarman, 24BS) the flak looked a little more deadly from his position:

The Mission number74 on Aug 8th is Yawata. It was a daylight precision against the urban area. Time over target around noon time. 245 A/C took off from the 58, 73 and 313 Wings. 221 A/C bombed the primary target. 100 A/C landed at Iwo for gas. The Japanese threw up a box barrage and we lost 4 A/C. The most dangerous mission I was ever on. The second most dangerous was trying to land at Iwo for gas. The only thing the B29 gave way for was two red flares (wounded on board). As I looked out after the bomb run I said “we went thru that” the flak was so thick it is a wonder we did not lose more.