British Prime Minister Winston Churchill called Italy the “soft underbelly” of the Axis, which may have been true politically, but certainly was not militarily as events were to prove. Yet, a military soft underbelly did exist, but it was in the Western Hemisphere: Central and South America. From the late 1930s, Germany and Italy had efficiently and thoroughly organized propaganda agencies throughout the region. This resulted in the election of a number of pro-Axis governments. With the United States taking an increasingly pro-Allied stance, the strategic threat to the Panama Canal, then under United States control, and shipping lanes off Brazil’s north-east coast – the “bulge” closest to Africa – were just two of an array of challenges faced by the United States seeking to secure its southern flank.

“We cannot take any chances with the Panama Canal. If it is blocked, our whole situation in the Atlantic becomes immensely critical should there be a tragic result in England.”

First and foremost, the United States had to protect the Panama Canal. Without it, the United States’ ability to operate a two-ocean navy would be severely compromised. In a confidential memo dated Jan. 24, 1941, to Lt. Gen. Daniel Van Voorhis, the Canal Zone’s military commander, Army Chief of Staff Gen. George Marshall wrote, in part, “We cannot take any chances with the Panama Canal. If it is blocked, our whole situation in the Atlantic becomes immensely critical should there be a tragic result in England.” Marshall had reason to be concerned with the situation there. Relations with Panama’s president, the openly pro-Axis Dr. Arnulfo Arias, had almost reached a breaking point.

Earlier that month, on Jan. 9, 1941, Secretary of War Henry Stimson met with President Franklin Roosevelt regarding security of the Canal Zone. In his diary Stimson called the Panamanian government “unfriendly” and wrote it was “refusing to give us, or delaying in giving us, the emergency landing fields and airdromes that we want in different parts of the Republic. All the planes which are necessary for the defenses of the Canal are crowded together in three small airdromes in a very small space and would be at the mercy of sudden attack from the air.”

Despite increased pressure from the United States, Arias drove a hard bargain and gained a number of economic concessions before agreeing in March 1941 to allowing the United States to build and develop additional Canal Zone defenses on Panamanian soil. A demagogue, Arias soon alienated powerful groups within Panama, and was ousted in a coup in October of that year.

Another country in the hemisphere that received a lot of attention from the War Department at this time was Brazil. In addition to its strategic location along the South Atlantic, Brazil was an important source of raw materials. Pro-Axis activity emanating from Germany’s Condor and Italy’s LATI airlines, which had extensive networks in Brazil and throughout the South American continent, was so widespread that Brazilian president Getulio Vargas was unable to control it.

In March 1941, the War Department embarked on an aggressive policy supporting Pan American Airways’ expansion of operations “until Axis-controlled lines had been eliminated in South America.” At the same time, blockade efforts designed to interdict additional aircraft, spare parts, and skilled workers shipped from Germany to Brazil were increased. The combined effort was so successful that by the time the United States entered the war in December 1941, Condor and LATI operations had all but ceased.

The War Department did not confine its efforts in Brazil to the air. In May of that year, in a confidential letter to Brig. Gen. Lehman W. Miller, the head of the United States Military Mission to Brazil, Marshall raised the idea of sending American squadrons to participate in military maneuvers scheduled by the Brazilian government. Addressing the issue of Brazilian sensitivities regarding American forces in its territory, Marshall wrote, “So long as we do not land combatant ground troops, and so long as the ground troops are the major participants and are local troops under local command, it seems to me that there is a chance of establishing a valuable precedent for cooperative action.”

But the subject proved so volatile that it was never implemented. Brazil would remain neutral until August 1942, when as a result of German U-boat sinkings of its shipping, Brazil declared war on the Axis, the first South American nation to do so.

Due to these and other diplomatic efforts guaranteeing substantial economic aid to Mexico and all the countries in Central and South America, the United States was able to accomplish its goal of preventing Axis hegemony in the Western Hemisphere.