«Buried Caesars» by Stuart Kaminsky

Toby joins forces with a famous PI to save a general from embarrassment.
The uniformed man standing before Toby Peters is General Douglas MacArthur, a soldier who considers himself the only man who can defeat the Japanese. But though he may be all-powerful in the South Pacific, today he is in Los Angeles with a problem only a detective can solve. The general has an eye on a post-war promotion to the White House, and an aide has stolen his war chest, his donor list, and a handful of embarrassing private letters. To get them back, Toby may need some help. Lucky for him, he's just met Dashiell Hammett, one of the finest crime novelists of all time. Dodging his mistress while he's waiting to rejoin the army, Dash needs amusement and thinks Toby's case sounds like a lark.
In fact, the assignment proves dangerous. Toby may not be a soldier, but he's finally gotten a chance to die at a general's whim.