This is a 2nd thread on the FEAF's Air Technical Intelligence Group (ATIG) Report No. 153 Japanese Radar Countermeaures. It covers Japanese radar dipole decoys in WW2 1/
This was the previous thread on Japanese radar intelligence.
This was the previous thread on Japanese radar intelligence.
https://twitter.com/TrentTelenko/status/1369805884994428930.
This is the part of the "Standard Narrative" of WW2 Japanese radar decoys from Alfred Price's PhD thesis on the IJA's use of radar decoys against a US radar in China. 2/ 
The late Dr Price was a both a great archival historian and as a officer on the RAF's electronic warfare desk in the 1960's. He knew everyone who was anyone in E.W. from that era.
But he didn't have ATIG No. 153 to read when he wrote his thesis or revised it in book form. 3/
But he didn't have ATIG No. 153 to read when he wrote his thesis or revised it in book form. 3/
Summarizing from ATIG No. 153. IJNAF & over all
1. The ATIG report does not have Price's China story at all.
2. The airfield that Price was referring to was protected by a SCR-636 radar operating at 212 Mhz that was malfunctioning immediately prior to the raid and had been 4/
1. The ATIG report does not have Price's China story at all.
2. The airfield that Price was referring to was protected by a SCR-636 radar operating at 212 Mhz that was malfunctioning immediately prior to the raid and had been 4/
...taken off the air for a lack of spare parts.
3. The the ATIG report says Japanese already had decoys cut to the SCR-636 frequency and reportedly never made any outside the lengths mentioned in the ATIG report. 5/
3. The the ATIG report says Japanese already had decoys cut to the SCR-636 frequency and reportedly never made any outside the lengths mentioned in the ATIG report. 5/
4. The Japanese navy had standardized and effective decoy laying tactics dating from the Solomons (1943).
5. The IJN had decoy dispensers in late 1943. 6/
5. The IJN had decoy dispensers in late 1943. 6/
6. After the Japanese losses to radar directed AA fire off Formosa in Sept 1944 -- which the 75cm chaff from their new window bombs didn't affect -- the Japanese assumed the Americans switched to 10cm AA fire control and cut new dipole decoys accordingly. 7/
7. Window bombs were used with night torpedo attacks dropped around a task force from 15 miles with six to nine planes carrying 30 such bombs.
Note: I have the USN reports on that air raid, & interestingly, they don't mention Japanese chaff. 8/
Note: I have the USN reports on that air raid, & interestingly, they don't mention Japanese chaff. 8/
8. The Japanese dropped 10cm dipole decoys at Iwo Jima (Feb 1945) and thought it "ineffective"
This was the 'Worst day in USN Fighter Direction vs the Kamikazes' where 6 IJN planes scored 5 bomb hits on the USS Saratoga in 3 minutes & CVE USS Bismark Sea was sunk
9/
This was the 'Worst day in USN Fighter Direction vs the Kamikazes' where 6 IJN planes scored 5 bomb hits on the USS Saratoga in 3 minutes & CVE USS Bismark Sea was sunk
9/
9. The Imperial Japanese navy was using both it's own "Rope" and were also recycling B-29 dropped Rope decoys over Okinawa.
10/
10/
IJAAF Radar Decoy Section from ATIG No. 153
10. The Japanese Army did their dipole decoy experiments in Feb 1943.
11. The Japanese Army got a German sample of window in June 1943.
11/
10. The Japanese Army did their dipole decoy experiments in Feb 1943.
11. The Japanese Army got a German sample of window in June 1943.
11/
12. The first "official" Japanese Army use of dipole decoys was Okinawa with 75cm and 25cm decoys. The latter for US Night fighters.
Note: 50cm was German AIA radar frequency, not US or UK. The USB had an airborne surface search radar at 57 CM.
12/
Note: 50cm was German AIA radar frequency, not US or UK. The USB had an airborne surface search radar at 57 CM.
12/
13 The Japanese Army never used 10cm dipole decoys
14 The standard Okinawa window load for a Japanese Army bomber or recon plane was 40 bundles of 300 strips of 75cm decoys.
15. The Japanese Army also was recycling B-29 dropped Rope decoys over Okinawa.
13/
14 The standard Okinawa window load for a Japanese Army bomber or recon plane was 40 bundles of 300 strips of 75cm decoys.
15. The Japanese Army also was recycling B-29 dropped Rope decoys over Okinawa.
13/
16. The Japanese army designed and ordered in Nov 1944 dipole decoy artillery shells, but the procurement got hung up in their bureaucracy.
14/
14/
17. Three Japanese companies started producing Window in Dec 1944 and completed 27 million 75cm strips by wars end. The monthly production rate was 1.2 million strips.
Note: It's not clear if that is total, or per company, as the numbers don't work out for 12-44 to 8-45.
15/
Note: It's not clear if that is total, or per company, as the numbers don't work out for 12-44 to 8-45.
15/
The implication I draw from 1-thru-3 is the IJA ferreted out that malfunctioning radar's signal (AKA the 225 Mhz, not 212 Mhz) and cut their chaff to match it immediately before the attack. They would have used standard 75cm chaff [1.5 meter wavelength is 200 Mhz frequency]. 16/
Where things in ATIG No. 153 get funny.
A. Section 22 reports mention IJN naval guns with chaff. There is no mention of same in ATIG No. 153.
B. There is nothing from RCM Digests 14, 19 or 20 regards all sorts of IJN radar dipole reflector decoys cut to various other
17/
A. Section 22 reports mention IJN naval guns with chaff. There is no mention of same in ATIG No. 153.
B. There is nothing from RCM Digests 14, 19 or 20 regards all sorts of IJN radar dipole reflector decoys cut to various other
17/
... wavelengths captured starting in June 1944 at Biak per Section 22 reports.
(See attached).
18/
(See attached).
18/
So...ATIG No. 153 has got that post-WW2 JCS budget, role & mission squeegee groove going.
Just not as much as other post-war reports
/End
Just not as much as other post-war reports
/End
P.S.
The above thread summaries are from the Section of ATIG No. 153 titled "Japanese Operational Use of Window" that is attached to this tweet.
The above thread summaries are from the Section of ATIG No. 153 titled "Japanese Operational Use of Window" that is attached to this tweet.
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