Labor conflicts and social unrest in the 1930’s spawned by the Great Depression created fear and concerns for public safety. Strikes by the longshoremen and teamsters in 1934 threatened to seriously disrupt business and normal life in Contra Costa County. Food deliveries were halted and frantic housewives stripped local grocery stores in order to stock up on several weeks supply of food. Even powerful Standard Oil of California (now ChevronTexaco) along with all the other oil companies shut down their refineries in the county fearing that terrorists would blow up their plants.
Pickets invaded Contra Costa stopping the delivery of oil and export of local farm products. Soon drivers were unable to buy gasoline and many could not get to their jobs. Some lost jobs as companies shut down for fear of reprisals. Philip Bancroft even equipped his pear produce truckers with shot guns and became famous statewide as the "Fighting Farmer of Walnut Creek." Stores that did obtain new supplies were afraid to display any of it in their windows for fear of retaliation.
Communists took a major role in promoting labor unrest in the Bay Area. Politicians in Contra Costa County therefore tended to view all strikers as radicals and Communists. The local newspapers and populace circulated rumors of Red gangs inflicting murder and plotting new bloodshed. In July of 1934, two hundred mayors, justices of the peace and law enforcement officers met in Martinez and requested that Governor Merriam call out the militia to "maintain order." Walnut Creek deputized forty local citizens charging them with "keeping the peace and preventing riots." The new deputies were also offered to farmers as armed protection for moving their produce to market. In Richmond private individuals invaded the residences of known Communists seeking out and destroying Party magazines and pamphlets.
In response to these events, many in Contra Costa felt even sterner measures were required. More than one hundred gathered in the Walnut Creek American Legion Hall and formed the Diablo Nationals. This was to be an armed home guard designed to "combat radicalism in every form whenever it crops up in central Contra Costa County." At its first rally in August 1934, Major Overton of the California National Guard spoke at great length on the evils of Communism as seen by him while visiting the Soviet Union.
Aside from meetings and rallies the Diablo Nationals found little to occupy their energies until January 24, 1935. There had been a scandal and investigation into the County Department of Social Services. The Board of Supervisors was scheduled to select a new Social Service Director. Rumors circulated through the county that Red agitators and their supporters from San Francisco would invade the Supervisor’s meeting and take over the proceedings. Under the direction of the county sheriff, the well armed Diablo Nationals and the Walnut Creek special deputies arrived in Martinez to "keep order" at the meeting. But whether for lack of interest by the Communists or the strong presence of the Diablo Nationals, no representatives of the Party ever appeared.
Although in later years confrontations between rival unions in Crockett and vicious strikes on ranches like the Balfour-Guthrie property led to violence, the perceived need for the Diablo Nationals gradually faded along with the 1930’s. Much of the local anti-radical activity was taken over by the Contra Costa Associated Farmers headed by Philip Bancroft. When a farm workers’ camp in eastern Contra Costa was surrounded by barbed wire and guards posted, the Associated Farmers explained that "obviously the fence and guards were there to keep the lawless element out, not to keep the contented workmen in." Today the Diablo Nationals exist only as an obscure historical footnote in a tumultuous era.