A Bitter Field by Jack Ludlow
1938. As Hitler sets his sights on the Sudetenland, not everyone in Britain is willing to appease him. Convinced that the Fuehrer's land-hunger is insatiable, the head of the SIS recruits Cal Jardine to help him prove zechoslovakia is threatened with invasion. Before heading undercover to Prague, however, Jardine must first extricate himself from France, where his attempts to smuggle guns to Spain have been held up by a group of fanatical fascists. In their struggle to overthrow the French government, they are prepared to kill for the sake of procuring weapons. Finally arriving in Czechoslovakia, working undercover for the SIS proves no less dangerous. As jealousy and mutual suspicions within Secret Service ranks make it impossible for Jardine to tell friend from foe, he rediscovers old friends of dubious loyalty and makes new enemies of untested ruthlessness.