In modern world history, in which year did the Second World War, also known as World War II, officially begin?

Introduction / Context:
World War II was one of the most destructive global conflicts in human history and is a central topic in modern world history. Examinations often ask simple factual questions about when major wars began and ended because these dates form the backbone of many other political, economic and social developments. This question checks whether you know the year in which World War II officially started, which also helps you differentiate it from World War I and the period between the two wars.

Given Data / Assumptions:

The question refers specifically to the Second World War, that is World War II.

It asks for the starting year, not the end year.

The options include years that are also associated with other important events, such as World War I and the end of World War II.

Concept / Approach:
To answer this, we need to recall a basic timeline of twentieth century conflicts. World War I began in 1914 and ended in 1918, with peace treaties signed around 1919. World War II began later, after a period of economic crisis and the rise of fascist regimes in Germany, Italy and elsewhere. The commonly accepted formal start of World War II is when Germany invaded Poland and the United Kingdom and France responded by declaring war. This took place in 1939, which is therefore the year we must choose.

Step-by-Step Solution:
Step 1: Recall that World War I started in 1914 and the peace treaties were signed around 1919. Step 2: Remember that there was a period between the two wars that included the Great Depression and the rise of Adolf Hitler in Germany. Step 3: Note that Germany invaded Poland on 1 September 1939. Step 4: The United Kingdom and France declared war on Germany shortly afterwards, marking the formal beginning of World War II. Step 5: Therefore, the accepted starting year of World War II is 1939, which matches option 1939.

Verification / Alternative check:
A quick verification is to pair the start and end years of the two world wars. World War I is remembered with the years 1914 to 1918. World War II is remembered with the years 1939 to 1945. Once you recall that the war ended in 1945, subtracting about six years gives 1939 as the start year, which matches the standard historical account. This cross check helps anchor the dates firmly in memory.

Why Other Options Are Wrong:
1914: This is the year when World War I began, triggered by the assassination of Archduke Franz Ferdinand of Austria. It does not mark the start of World War II.
1919: This year is associated with the Treaty of Versailles and the formal peace settlements that followed World War I. It is in the interwar period, not the start of World War II.
1945: This is the year World War II ended, with Germany s surrender in May and Japan s surrender after the atomic bombings in August. It is the end year, not the start year.

Common Pitfalls:
Students sometimes confuse the start years of the two world wars or mix up start and end years. One way to avoid this is to remember them as pairs: World War I is 1914 to 1918 and World War II is 1939 to 1945. Another mistake is to think that the war started when the first aggressive actions began in the 1930s, such as the occupation of certain territories, but the officially recognised global conflict date is linked to the invasion of Poland in 1939. Keeping these simple anchor points in mind will help you answer many related questions quickly in exams.

Final Answer:
World War II officially began in the year 1939.