Jonathan Parshall:

Every IJN fan's favorite whipping-boy admiral, and hey, why should I be any different? Gruff, conservative, not overly-imaginative, and at his core profoundly suspicious of the potency of carrier-based airpower, Nagumo was (ironically enough) placed in charge of the most powerful naval air armada of the first half of the war: Kido Butai, Japan's carrier strike force. He was in charge of executing Yamamoto's plan for a Pearl Harbor attack, which was also ironic, because he and Yamamoto got along very poorly, and Nagumo didn't believe in Yamamoto's plan at all. The result; a spectacular, but somewhat superficial victory in Hawaii, wherein the US heavy surface units were largely destroyed or disabled, but escort vessels and (much more important) oil tanks farms and repair facilities escaped practically untouched (despite the urging of his staff officers to launch a second attack and destroy them). This, in turn, left the US Navy with both the carrier escorts and the logistical underpinnings necessary to carry on the war.

After Pearl Harbor, Nagumo commanded Kido Butai through its subsequent six-month long reign of terror, during which it roamed the Pacific with seeming invincibility, until it was finally dismembered at the Battle of Midway. Thereafter he went on to lead the Combined Fleet's carrier aviation forces through a series of uninspiring performances around the Solomons, finally being removed from command after the Battle of Santa Cruz, October 25-27, 1942. He died by his own hand during the invasion of Saipan in July, 1944.

C. Peter Chen:

For an officer of the old school, who believed in the ways of the big gun more than aircraft, it was a surprise that he was placed in charge of a carrier group. Sure he was among the hardest working admirals in the navy, but his innate distrust of naval aviation seemed to lead him to certain doom. This was where his leadership and experience came into play. In the first six months of the Pacific War, he racked up the most impressive resume in the history of naval warfare:

• He had sailed from Kurile Islands to Pearl Harbor, returned to the western portion of the South Pacific, and then sailed into the Indian Ocean.
• He had destroyed five battleships, one carrier, two cruisers, seven destroyers, dozens of merchantmen, transports, and various other vessels.
• He was responsible for destroying hundreds of aircraft from six nations.
• He brought destruction upon Allied ports, disabling or slowing Allied operations.
• The damage brought upon Allied forces were at a cost of no more than a few dozen pilots.

Of course, the failure at the Battle of Midway allowed Yamamoto, who had not been a supporter of Nagumo, to remove him from power. After Midway, he held much less important posts and largely faded away from history.

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WW2DB biography of Chuichi Nagumo