Study this source. Source C 'I am writing this from a village 40 kilometres west of Moscow. The temperature is minus 35 degrees. Our vehicles will not start...

Understanding the question type: 'How far does this source prove...?' asks you to evaluate whether the source provides sufficient evidence for the claim. You must use specific details from the source to support the claim, then test its limits by considering what the source leaves out and what your own knowledge adds.

What the source says: The source is a letter from a German infantry officer to his wife, written in December 1941. He describes his position 40 kilometres west of Moscow in temperatures of minus 35 degrees. His vehicles will not start, machine guns jam, and his men have only summer uniforms issued in June with nothing warmer since. Soldiers wrap themselves in carpets from Russian houses. His company has been reduced from 180 men to 53 fit for duty; the rest are dead, wounded, or suffering from frostbite. He states that the High Command assured them the campaign would be over before winter, and 'they were wrong.'

How the source supports the claim of failure:

• The officer is only 40km from Moscow but clearly cannot advance further. The proximity to the objective combined with the inability to reach it captures the essence of Barbarossa's failure.
• His company has lost over 70% of its strength (from 180 to 53), illustrating the unsustainable attrition rate.
• Equipment failures at minus 35 degrees show that the German war machine was not designed for a winter campaign. The lack of winter clothing confirms catastrophic logistical planning.
• The admission that the High Command 'were wrong' about a quick victory directly states that the original objective of rapid conquest had failed.

Limitations of the source as 'proof' of failure:

• One officer's experience: The letter represents a single company on one sector of the front. Conditions may have varied across the vast Eastern Front, which stretched over 2,800 kilometres.
• Timing matters: Written in December 1941, the letter captures a snapshot. The Soviet counter-attack on 5 December 1941, using fresh Siberian divisions transferred after intelligence confirmed Japan would not attack the Soviet Union, pushed the Germans back 100 to 250 kilometres from Moscow. This confirms the source's picture of crisis, but the officer may not yet have known about it.
• Barbarossa was not a total military failure at this point: By December 1941, Germany had achieved enormous territorial gains: Ukraine's grain-producing regions, the Donbas industrial basin, and vast areas of western Russia were under German control. Over 3 million Soviet soldiers had been killed or captured. The campaign failed in its original objective of rapid victory, but it did not immediately lose the war for Germany.
• The war continued: Hitler shifted objectives in 1942 to Stalingrad and the Caucasus oil fields, showing that Germany retained offensive capacity. The decisive defeat came later, at Stalingrad (February 1943) and Kursk (July 1943).

Reaching a judgement: The source powerfully illustrates that Barbarossa had failed in its original aim of defeating the Soviet Union before winter. However, 'failure' is a matter of degree. The campaign failed as a war-ending blow but succeeded in inflicting massive damage on the Red Army and occupying enormous territory. A more precise assessment is that Barbarossa failed to achieve its decisive objective, but it had not yet resulted in Germany's defeat.

Mark scheme breakdown:

• Level 1 [1-2 marks]: Simple agreement, such as 'Yes, it proves Barbarossa failed because the soldiers were cold.'
• Level 2 [3-5 marks]: Uses source details to address the claim. Identifies specific evidence of failure (proximity to Moscow without being able to advance, loss of 70% of the company, equipment failure, admission that the High Command was wrong) but may not balance with limitations.
• Level 3 [6-8 marks]: Balanced evaluation using source details and own knowledge. Explains what the source shows about Barbarossa's failure (logistical collapse, casualty rates, failure to take Moscow) while noting its limits (one officer's view, enormous territorial gains by Germany, the war continuing beyond this moment). Reaches a supported judgement about 'how far' the source proves the claim.

Exam tip: When a question says 'how far does this source prove,' the examiner wants you to evaluate the strength of the evidence, not just agree or disagree. Consider what 'proof' requires: a single eyewitness account is powerful but narrow. Always ask what the source cannot tell you and whether your own knowledge confirms or complicates the picture.