Drawing on US/Japanese military archives and other extensive research, Coppel (The Hastings Conspiracy, The Apocalypse Brigade) imagines here what would have happened if the A-bomb had not been technically usable in the summer of 1945--with the implication that Hiroshima/Nagasaki was the preferable alternative by far. In November 1945 ""Operation Olympic"" takes the island of Kyushu--with heavy casualties. (""The entire nation was now resolved to offer itself as a sacrifice."") Then, the bulk of the novel: ""Operation Coronet,"" the assault on Honshu in February/March 1946. Coppel dramatizes this fantasy-history in scores of vignettes featuring dozens of US and Japanese servicemen: Marines, pilots (kamikaze and otherwise), submarine officers, soldiers, radar-men, etc. There are also fleeting glimpses of Nimitz, MacArthur, and the coup that brings Tojo back to power (putting the end to any hopes of an early Japanese surrender). But none of the characters receives enough attention or development to give the military mockup an emotionally involving thread--and the result is, for the most part, a disjointed series of moments-in-combat. Among the more fully realized mini-plots: a US bombardier parachutes into a rice paddy and is taken prisoner by sadistic Japanese; a Japanese POW is better treated but murdered by a Korean; US invaders face fierce, virtually suicidal opposition from civilians; a bloodthirsty Air Force Major is horrified by a kamikaze attack on the USS Solace; and Japanese-raised Lieut. Harry Seaver winds up, via the inevitable coincidence, facing his boyhood chum Kantaro Maeda in battle. (Harry will ritually behead the dying Kantaro, then sleep with Kantaro's sister.) According to Coppel's imaginary warfare, however, the invasion is slowed--by bad weather, huge casualties, and those maniacally combative civilians. So President Truman must again face the A-bomb decision--and reaches, ironically, the same decision he did in 1945. Minimal appeal, then, for the mainstream WW II fiction audience; but those who dote on fanciful military-history will appreciate Coppel's elaborate detailing of geography, weaponry, and battleground gore--even if it's diluted by all those ineffectual, skimpily-sketched characterizations.