London, England April 13, 1939

Following the Nazi occupation of Czecho­slo­va­kia’s Ger­man-speaking Sude­ten­land in Octo­ber 1938 and the in­va­sion and in­cor­po­ra­tion of the rest of Czecho­slo­va­kia into the Reich in mid-March 1939, Great Britain, France, Poland, Greece, and Roma­nia entered into mutu­al assist­ance pacts in case of a mili­tary in­va­sion by “a Euro­pean power,” meaning Ger­many. In early April 1939 the part­ners con­sisted of just Brit­ain, France, and Poland, although the three nations had not yet com­mitted them­selves to formalizing the arrangement.

On this date, April 13, 1939, Britain and France guaran­teed the bor­ders of Roma­nia and Greece fol­lowing Italy’s inva­sion of tiny Alba­nia, Greece’s neigh­bor to the north, pledging to lend “all sup­port pos­sible” where there were clear threats to the inde­pend­ence of either coun­try. On August 25, 1939, two days after the for­eign minis­ters of the Soviet Union and Ger­many had signed the Molo­tov-Rib­ben­trop Non­ag­gres­sion Pact, Britain and Poland ini­tialed the Agree­ment of Mutu­al Assis­tance. The agree­ment con­tained pro­mises of mutual mili­tary assis­tance between the nations in the event either was attacked by some “Euro­pean country,” the name of which was spelled out in a secret proto­col of the pact—Ger­many. The French govern­ment waited until Septem­ber 4, 1939, one day after declaring war on Ger­many, to ratify a secret proto­col to the 1921 Franco-Polish mili­tary alliance that had been signed the previous May.

After Germany’s conquest of Poland (1939); the Low Coun­tries, Den­mark, Nor­way, and France (1940); Greece and Yugo­sla­via (1941); and the enlarge­ment of the Axis Tri­par­tite Pact by Roma­nia, Hun­gary, and Slo­va­kia (Novem­ber 1940), Britain stood prac­ti­cally alone against the Nazi bully. The single excep­tion was Ger­many’s erst­while treaty part­ner, the Soviet Union, since June 22, 1941, the object of Adolf Hitler’s colos­sal and suici­dal mili­tary cam­paign in the east—Opera­tion Barba­rossa. When Ger­many and Italy foolishly joined Japan in declaring war against the United States in Decem­ber 1941, the pro­duct­ion, finan­cial, and pro­spec­tive mili­tary might of Amer­ica was thrown into the balance against the Axis. British Prime Minis­ter Winston Chur­chill expressed his relief at the turn of events, writing, “[T]o have the United States at our side was to me the greatest joy. . . . [T]o know the United States was in the war, up to the neck and in to the death. So we had won after all!” Churchill would even­tually be proven right, of course, but the human cost was cata­strophic and dispro­por­tionate—between 2.5 and 3 percent of the world’s popu­la­tion died in the global conflict, civilians accounting for two-thirds of the dead.

Scenes of German Military Incursions in European Cities, 1940–1941, and Aftermath

German military incursions in Europe: German assault on Warsaw, 1939German military incursions in Europe: German assault on Norwegian village, 1940

Left: German forces enter Poland’s capital, Warsaw, late September 1939. The Ger­man occu­pa­tion of Poland was one of the most bru­tal epi­sodes of World War II, resulting in the deaths of roughly 20 per­cent of the coun­try’s 34.8 mil­lion in­hab­i­tants (1939 est.) and over 90 per­cent of its Jewish minority.

Right: German infantry attacking through a burning Nor­we­gian vil­lage 25 miles west of Lille­ham­mer, April 1940. In a coun­try that had a pop­u­la­tion of barely 3,000,000, the Wehr­macht garri­soned some 300,000 troops in Nor­way for the next five years in col­lab­o­ra­tion with the pup­pet govern­ment of Vid­kin Quis­ling. In the northern part of the country, where Soviet armed forces pressed their attack in 1944 and early 1945, the Germans employed a scorched earth policy, leaving over 70,000 people home­less and denying the inhab­i­tants and the enemy food, boats, roads, and commu­ni­ca­tion lines in the area. Out of an esti­mated 2,173 Jews in Norway in 1940, at least 765 died, 742 of them murdered in concentration camps.

German military incursions in Europe: Destroyed Rotterdam RR stationGerman military incursions in Europe: German troops in Paris, June 1940

Left: Rotterdam’s central Blaak railway sta­tion de­stroyed on May 14, 1940, during the Ger­man terror bombing of Rot­ter­dam (“Rot­ter­dam Blitz”), which killed 800–900 Dutch civil­ians and de­stroyed 25,000 homes. By the end of the war, 205,901 Dutch men and women had died of war-related causes. Over half were Holo­caust victims. Of the 140,000 Jews who had lived in the Nether­lands before 1940, only 30,000 (21 per­cent) sur­vived the war, a much lower per­cent­age compared with neighboring Belgium and France.

Right: German troops enter Paris, France, June 1940. Pro­tecting their home­land during the Battle of France, the French suffered 2.26 mil­lion casual­ties, of which 360,000 were killed or wounded. Pri­soners of war and deportee totals were around 1,900,000. Of this, around 240,000 died in cap­tiv­ity. By the time of their liber­a­tion, some 580,000 French had died out of a pop­u­la­tion of 35.5 mil­lion (1940). Of the 350,000 Jews who lived in France in 1940, up­wards of 90,000 died during the war, most (over 73,000) as deportees in German concentration camps.

German military incursions in Europe: Damaged street in Belgrade, 1941German military incursions in Europe: German reinforcements enter Athens, May 1941

Left: Damaged street in Yugoslavia’s capital, Belgrade, 1941. On April 6, 1941, Hitler mer­ci­lessly ordered the Yugo­slav capi­tal Bel­grade be bombed days after regent Prince Paul, who had initialed the Axis Tri­par­tite Pact the month before, was deposed in a coup d’état and his young nephew Peter II pro­claimed of age. When the air attack was over, some 4,000 Bel­grade inhab­i­tants lay dead under the rubble. During World War II a little over one mil­lion Yugo­slavs out of a pop­u­la­tion of 13.9 mil­lion (1931 est.) became casual­ties (slightly more Par­ti­sans than col­lab­o­ra­tors), of whom 581,000 were civil­ian losses. Some 57,000 Jews, who made up less than one per­cent of the population, perished.

Right: German reinforcements enter Greece’s capital, Athens, May 1941. Greece’s civil­ian pop­u­la­tion of over seven mil­lion suffered horri­bly under Axis occu­pa­tion. In Athens alone more than 300,000 civil­ians died from star­va­tion, and tens of thou­sands more died in repri­sals by Ger­mans and their Greek col­lab­o­ra­tors. At least 81 per­cent (ca. 60,000) of Greece’s total pre­war Jewish popu­lation died during the occupation.

Operation Marita: Nazi Germany’s Attack on Greece, April 1941