Germany was disarmed after World War I with the signing of the Treaty of Versailles. Rearmament started off as a small, covert operation which expanded massively after the Nazi Party took power in 1933. Germany viewed the Treaty of Versailles as an economic anticompetitive measure. Large industrial companies went from producing domestic products to producing war material and aircrafts. 

The Rhineland was a part of German territory that was demilitarized and served as a buffer between Germany and the western powers. Germany  As part of the Treaty of Versailles, Germany was "forbidden to maintain or construct any fortification either on the Left bank of the Rhine or on the Right bank to the west of a line drawn fifty kilometers to the East of the Rhine". The Treaty also stated that any violation of the Treaty would be considered a hostile act. 

In 1936, the Spanish Army revolted against the government. There were 2 groups the Nationalists and the Republicans. The Nationalists were made up of the army, catholics, and other conservatives. The Republicans were made up socialists, republicans, anti-church people, and communists. Italy and Germany backed the Nationalists and the USSR supported the Republicans. Britain and France tried to stop things by suggesting an arms embargo which Germany and Italy both agreed to but secretly continued to support the civil war. 

The four year plan aimed to 

The German-Soviet Aggression Pact was signed in August 1939. Under this pact, Germany and the Soviet Russia agreed not to take any military action against one another. 

Collective security, system by which states have attempted to prevent or stop wars. Under a collective security arrangement, an aggressor against any one state is considered an aggressor against all other states, which act together to repel the aggressor. Collective security arrangements have always been conceived as being global in scope; this is, in fact, a defining characteristic, distinguishing them from regional alliances such as the North Atlantic Treaty Organization. Both the League of Nations and the United Nations were founded on the principle of collective security. Neither the League nor the United Nations were able to operate the principle successfully to prevent aggression because of the conflicts of interest among states, especially among the major powers. The existence of such conflicts has in fact been recognized in the institutionalized arrangements of the two world bodies themselves: under the Covenant of the League of Nations the response to aggression was left to the member states to decide, and under the UN Charter any permanent member of the Security Council may veto collective action.

Instituted in the hope of avoiding war, appeasement was the name given to Britain’s policy in the 1930s of allowing Hitler to expand German territory unchecked. Most closely associated with British Prime Minister Neville Chamberlain, it is now widely discredited as a policy of weakness. Yet at the time, it was a popular and seemingly pragmatic policy. Hitler’s expansionist aims became clear in 1936 when his forces entered the Rhineland. Two years later, in March 1938, he annexed Austria. At the Munich Conference that September, Neville Chamberlain seemed to have averted war by agreeing that Germany could occupy the Sudetenland, the German-speaking part of Czechoslovakia - this became known as the Munich Agreement. In Britain, the Munich Agreement was greeted with jubilation. However, Winston Churchill, then estranged from government and one of the few to oppose appeasement of Hitler, described it as ‘an unmitigated disaster’. Appeasement was popular for several reasons. Chamberlain - and the British people - were desperate to avoid the slaughter of another world war. Britain was overstretched policing its empire and could not afford major rearmament. Its main ally, France, was seriously weakened and, unlike in the First World War, Commonwealth support was not a certainty. Many Britons also sympathised with Germany, which they felt had been treated unfairly following its defeat in 1918. But, despite his promise of ‘no more territorial demands in Europe’, Hitler was undeterred by appeasement. In March 1939, he violated the Munich Agreement by occupying the rest of Czechoslovakia. Six months later, in September 1939, Germany invaded Poland and Britain was at war.

The Sudetenland crisis began in February 1938 when Hitler demanded self-determination for all Germans in Austria and Czechoslovakia. Shortly after, Austrian Nazis rioted and invited Hitler to invade, which he did in March, declaring Anschluss. It was clear that Hitler wanted to do the same in Czechoslovakia. The Sudeten Nazi Party was causing strikes and riots. This was a direct threat to Czechoslovakia, which would lose its industrial areas and defendable frontiers. Chamberlain hinted that an invasion of Czechoslovakia would ‘possibly’ involve other countries. Tension ran so high that, in May 1938, the Czech government mobilized its army, thinking that the Germans were about to invade. In June 1938, the German Sudeten Party did well in the Czech national elections. It held talks with the Czech President Beneš, but these broke down in September. The Sudeten Germans demanded union with Germany, and caused so much trouble that the Czechs were forced to impose martial law. German newsreels showed ‘evidence’ of Czech ‘atrocities’ against the Sudeten Germans. Hitler threatened to support the Sudeten Germans with military force. Then Chamberlain intervened. On September 15 he met Hitler at Berchtesgaden. Hitler threatened war, but promised him that this was the ‘last problem to be solved’. Chamberlain decided that Hitler was ‘a man who can be relied upon’. He met for talks with the French, and together they persuaded the Czechs to agree to hand over the Sudetenland. But when Chamberlain met Hitler again to tell him – at Bad Godesberg – there were more demands. Hitler said that other Czech lands had to be given to Hungary and Poland, and that the Sudetenland should be occupied by Germany before October 1st. He assured Chamberlain that he had ‘no more territorial ambitions in Europe’. Chamberlain refused. War seemed near, but Chamberlain was not sure that Czechoslovakia was one of the ‘great issues’ which justified war. Instead, he decided that it was ‘a quarrel in a far-away country between people of whom we know nothing’. At Munich, Britain and France gave the Sudetenland to Germany. Czechoslovakia was not even invited to the talks. Chamberlain returned to England with his famous piece of paper. ‘I believe it is peace for our time’, he told the cheering crowd. The Czechs were free to fight if they wished, but they would have no support. They chose not to fight. In October 1938, Hitler marched into the Sudetenland unopposed.

The Pact of Steel, or formally the Pact of Friendship and Alliance between Germany and Italy, was an agreement between Fascist Italy and Nazi Germany signed on May 22, 1939, by the foreign ministers of each country and witnessed by Count Galeazzo Ciano for Italy and Joachim von Ribbentrop for Germany. There are two parts in the Pact. The first section was the formal text which said that the two would continue helping each other, while the second, the two agreed to make their military and economy policies to be the same way. It was said to be a "Secret Supplementary Protocol". The name of the Pact came from Italian leader Benito Mussolini who thought that its original name, "the Pact of Blood", would likely less popular in Italy.

The League of Nations was the first intergovernmental organization that was established after World War I in order to try and maintain the peace. Unfortunately the League failed miserably in its intended goal: to prevent another world war from happening (WWII broke out only two decades later). The idea was for the League of Nations to prevent wars through disarmament, collective security and negotiation. It was also involved in other issues such as drug trafficking, arms trade, and global health. Although the League disbanded during WWII, it was replaced with the United Nations, which is still going strong today.