Operation I-Go: Yamamoto’s Last Offensive—New Guinea and the Solomons, April 1943

Reviewed by Jeff Schultz

Michael Claringbould’s Operation I-Go: Yamamoto’s Last Offensive — New Guinea and the Solomons, April 1943 skillfully utilizes Japanese and Allied sources to thoroughly investigate Operation I-Go, an aerial operation set against the backdrop of the March-April 1943 Pacific War. While this ambitious operation employed a large number of Imperial Japanese Navy aircraft, it did not achieve what Admiral Yamamoto hoped, nor did it reckon with rising operational limitations or the growing Allied threat.

Claringbould is an accomplished and prolific Australian author with a number of World War II-related works to his credit such as two four-part series: Pacific Adversaries (2019-2021) and South Pacific Air War (2017-2019) and The Empire Strikes South: Japan’s Air War Against Northern Australia 1942-45 (2017), among others. His efforts in producing works using long-overlooked Japanese primary sources are of particular note, such as his seminal Eagles of the Southern Sky: The Tainan Air Group in WWII Volume One: New Guinea (2012).

The 158-page book is divided into seven chapters with four appendices, a postscript, a list of sources and an index well-supported with period black and white photos along with color maps. There are three larger foci of the chapters: first, Chapters 1 and 2 deal with the introduction and the effort to amass the planes used in Operation I-Go; secondly, Chapters 3 and 4 deal with the Japanese “Strike X”, both the attacks themselves and then the Allied response; and lastly Chapters 5, 6, and 7 discuss the three different Japanese attacks (as “Strike Y,” “Y1” and “Y2”) mounted against scattered Allied targets in southeast Papua New Guinea. The “Postscript” follows which offers analysis and insights. Throughout the book are excellent maps showing the airfields used, the target areas and descriptions of battle which elevate the work owing to visual cues which are often missing in battle histories. Interspersed through the work are primary source excerpts woven into the narrative along with references to wartime records, particularly regarding claims of planes shot down by both sides. As Claringbould notes in his concluding comments, the very nature of wartime “aces” comes into question when confronted with the disproportionate ratio of losses claimed to those actually suffered based on records comparison. This raises an important question: should the historical record be set straight, thereby reducing the “kill” totals of wartime aces, or left unchallenged, thereby protecting reputations built on the inflated long-claimed “kill” totals?

In Chapters 1 and 2, Claringbould helps set the stage for the operation, which was born out of a need to strike back but constrained by the reality of recent defeats. These prior losses culminated in the March 1943 Battle of the Bismarck Sea, which showed how decisive Allied airpower had become since the war began. The destruction of the critical convoy helped to end Japanese designs in Papua New Guinea and could not be ignored, especially the lackluster performance of the fighter units which failed to protect the doomed ships. The book gives good coverage of the Japanese limitations going into I-Go, which helps to slay the myth of the invincible Japanese warrior and bring him back to what he was, just as frail as the Allied personnel he faced. The main inspiration Isoroku Yamamoto brought to bear in the planning of I-Go concerned carrier aviation. After suffering dreadful losses at Midway in 1942, the quality of Imperial Japanese Navy (IJN) carrier airpower would never again be as effective but they were often better than the battle worn ground-based IJN air units which also suffered from poor morale and other consequences of operating in tropical disease-riddled areas. Land-based G4M “Betty” medium bombers were also minor players due to heavy losses, which could have brought more ordnance to bear. I-Go would not use any Imperial Japanese Army (IJA) air units, instead constituting an IJN only operation. As with many militaries, interservice rivalry haunted the Imperial Japanese along with too much wishful thinking.

In Chapters 3 and 4 Claringbould sketches out the initial attacks by IJN air units operating from Rabaul, Kavieng and other locations in the Solomon Islands against Allied shipping in and near Guadalcanal, collectively called “Strike X.” The planes that actually carried out the strikes comprised just a few types: A6M “Zeroes,” D3A “Vals” and a few other supporting types such as Ki-46 “Dinah” recon and a mix of armed floatplanes on the periphery. The weather, in particular, along with range limitations played an important role in all of the attacks in the book. If the weather seemed favorable, the range to target greatly impacted what ordnance the attacks carried. Specifically, the “Val” dive bombers could handle either a single powerful 250kg (550lb) centerline bomb or two 60kg (132lb) bombs with a drop tank on the centerline hardpoint. In “Strike X” some “Vals” were armed with 250kg bombs, while in the later “Strike Y” attacks this was difficult due to range. While the Japanese did sink a few ships during “Strike X”, such as the oiler USS Kanawha (AO 1) and destroyer Aaron Ward (DD 483), they also lost 24 planes so it would be challenging to argue it was a success. 

In Chapters 5, 6, and 7 Claringbould discusses the three different Japanese attacks (“Strike Y,” “Y1” and “Y2”) which were launched against three different locations in Papua New Guinea. “Strike Y,” meant to engage shipping at Oro Bay, damaged a few Allied vessels at the cost of five aircraft lost. “Strike Y1” attacked a number of airfields with arguably the largest ever raid on Port Moresby by 54 “Betty” medium bombers escorted by 132 “Zeroes,” against nearby airfields which destroyed six Allied planes on the ground and three in the air for the loss of eight “Bettys.” Lastly, “Strike Y2” included a mixture of high (“Betty”) and low (“Val”) bombers attacking shipping in Milne Bay, which failed to cause any major losses to the Allies although it did sink or damage some vessels such as the Dutch merchant vessel van Heemskerk for the loss of nineJapanese planes. As a common theme, however, the Japanese did not inflict major damage to any of the targets, yet suffered considerable losses, which they could ill afford. Finally, after the lackluster I-Go missions concluded, the Japanese lost its revered architect, when on 18 April 1943, American P-38 fighters ambushed Admiral Yamamoto’s “Betty” bomber and not only killed an irreplaceable leader but badly damaged Japanese morale.  

Michael Claringbould’s Operation I-Go: Yamamoto’s Last Offensive—New Guinea and the Solomons, April 1943offers readers yet another fine Pacific War-themed book which includes a crisp, yet brief analysis of Admiral Yamamoto’s last operation. His sagacious inclusion of Japanese sources provides much more context than previous histories which featured the Allied version of events and did not delve into detail regarding factors which influenced the Japanese failures, such as disease, training difficulties and crushing attrition. With the addition of a number of illustrations, this book is a great resource for those interested in the 1943 New Guinea/Solomons campaign, whether aviators, airplane modelers or general aviation history enthusiasts.


Jeff Schultz is an Associate Professor of History at Luzerne County Community College.

Operation I-Go: Yamamoto’s Last Offensive—New Guinea and the Solomons, April 1943 (Michael Claringbould, Avonmore Books, Australia, 2020).

Spread the word. Share this post!

Leave Comment

Your email address will not be published. Required fields are marked *