"Churchill was at pains to say in his memoirs that he was never going to negotiate with Germany, but it is clear that in 1940 he had not ruled out talking to a non-Hitler German government," said Professor Reynolds. ... This too was played down when Churchill came to writing The Second World War.
I believe it's the <span>Treaty of Brest-Litovsk, correct me if I'm wrong. </span>
Airplanes were used to get a clearer view on the battlefield, as well as using weapons to separate enemy troops.
To cause a source to be biased means that it is influenced by your opinion or another factor that is not factual. Bias can take away from the credibility because it is not completely true, as a source should be.
