Composed of three Royal Navy cruisers, HMS Exeter, Ajax, and Achilles, the unit was patrolling off the River Plate estuary of Argentina and Uruguay.

After negotiations with Brazilian Foreign Minister Osvaldo Aranha (on behalf of dictator Getúlio Vargas), the U.S. introduced its Air Force along Brazil's coast in the second half of 1941.

[4] After a series of attacks on merchant vessels off the Brazilian coast by U-507,[4] Brazil officially entered the war on 22 August 1942, offering an important addition to the Allied strategic position in the South Atlantic.

[7] Brazil saw three of its warships sunk and 486 men killed in action (332 in the cruiser Bahia); 972 seamen and civilian passengers were also lost aboard the 32 Brazilian merchant vessels attacked by enemy submarines.

The 33 German agents who formed the Duquesne spy ring were placed in key jobs in the United States to get information that could be used in the event of war and to carry out acts of sabotage.

The ring was led by Captain Fritz Joubert Duquesne, a South African Boer who spied for Germany in both World Wars and is best known as "The man who killed Kitchener" after he was awarded the Iron Cross for his key role in the sabotage and sinking of HMS Hampshire in 1916.

[16] After declaring war on the United States following the attack on Pearl Harbor, Adolf Hitler ordered the remaining German saboteurs to wreak havoc on America.

They were ordered to place mines in four areas: the Pennsylvania Railroad in Newark, New Jersey; canal sluices in both St. Louis, Missouri, and Cincinnati, Ohio; and New York City's water supply pipes.

[19] Dasch (aka George Davis), who had been a longtime American resident before the war, suffered a difficult life in Germany after his return from U.S. custody because he had betrayed his comrades to the U.S. authorities.

As a condition of his deportation, he was not permitted to return to the United States, even though he spent many years writing letters to prominent American authorities (J. Edgar Hoover, President Eisenhower, etc.)

His mission, codenamed Operation Grete, after the name of the agent's wife, was to observe and report shipping movements at Montreal and Halifax, Nova Scotia (the main departure port for North Atlantic convoys).

There Annett grew more suspicious and he alerted a Quebec Provincial Police constable, Alfonse Duchesneau, who quickly boarded the train as it pulled away from the station and began searching for the stranger.

For example, John Cecil Masterman wrote in The Double Cross System: "In November, WATCHDOG was landed from a U-boat in Canada together with a wireless set and an extensive questionnaire.

"[27] Accurate weather reporting was important to the sea war and on September 18, 1943, U-537 sailed from Kiel, via Bergen, Norway, with a meteorological team led by Professor Kurt Sommermeyer.

The only documented World War II sinking of a U-boat close to New England shores occurred on May 5, 1945, when the German submarine U-853 torpedoed and sank the collier Black Point off Newport, Rhode Island.

[34] From the start of the war in 1939 until VE Day, several of Canada's Atlantic coast ports became important to the resupply effort for the United Kingdom and later for the Allied land offensive on the Western Front.

Both ports were heavily fortified with shore radar emplacements, searchlight batteries, and extensive coastal artillery stations all manned by RCN and Canadian Army regular and reserve personnel.

Military intelligence agents enforced strict blackouts throughout the areas and anti-torpedo nets were in place at the harbor entrances, making a direct attack on those facilities unfeasible because it was impossible for Germany to provide air support.

On June 3–4, 1942, Japanese planes from two light carriers Ryūjō and Jun'yō struck the U.S. against the city of Unalaska, Alaska, at Dutch Harbor in the Aleutian Islands.

Attu's population at the time consisted of 45 Alaska Native Aleuts, and two white Americans – Charles Foster Jones, a 60-year-old ham radio operator and weather observer, and his 62-year-old wife Etta, a teacher and nurse.

The continental United States was first shelled by the Axis on February 23, 1942, when the Japanese submarine I-17 attacked the Ellwood Oil Field west of Goleta, near Santa Barbara, California.

On June 20, 1942, the Japanese submarine I-26, under the command of Yokota Minoru,[41] fired 25–30 rounds of 5.5-inch shells at the Estevan Point lighthouse on Vancouver Island in British Columbia, but failed to hit its target.

One member of the 555th Parachute Infantry Battalion died while responding to a fire in the Umpqua National Forest near Roseburg, Oregon, on August 6, 1945; other casualties of the 555th were two fractures and 20 other injuries.

The head of the Science Division of the Wehrmacht, Erich Schumann, lobbied for Hitler to be persuaded otherwise: "America must be attacked simultaneously with various human and animal epidemic pathogens, as well as plant pests."

During the final months of World War II, Japan had planned to use bubonic plague as a biological weapon against U.S. civilians in San Diego, California, during Operation Cherry Blossoms at Night.

[52] On December 8, 1941, "rumors of an enemy carrier off the coast led to the closing of schools in Oakland, California," a blackout enforced by local wardens and radio silence followed that evening.

Wall Street had its worst sell off since the Fall of France, school children in New York City were sent home and several radio stations left the air.

[52] In Boston police shifted heavy stores of guns and ammunition from storage vaults to stations throughout the city, and industrial establishments were advised to prepare for a raid.

[53][54] Initially, the target of the aerial barrage was thought to be an attacking force from Japan, but Secretary of the Navy Frank Knox speaking at a press conference shortly afterward called the incident a "false alarm."

When documenting the incident in 1983, the U.S. Office of Air Force History attributed the event to a case of "war nerves" likely triggered by a lost weather balloon and exacerbated by stray flares and shell bursts from adjoining batteries.