In 1939, Germany attempted to negiate various economic and political deals with the Soviet Union specifically having to do the trade mission in Praque and with the political question of what to do with Poland leading up to the Three Power Pact. Reading the various memoranda between foreign office secretaries and ambassadors is vivid stuff.
BERLIN, May 30, 1939.
No. 101. For the Ambassador.
Contrary to the policy previously planned, we have now decided to undertake definite negotiations with the Soviet Union. Accordingly, in the absence of the Ambassador I asked the Chargi, Astakhov, to see me today. The Soviet request for further continuance of their trade mission at Prague as a branch of the trade mission at Berlin provided the starting point of our conversation. Since the Russian request presents a question of policy the Reich Foreign Minister had also been considering it and he had taken the matter up with the F|hrer. To my inquiry as to whether the maintenance of the trade mission at Prague involved a permanent situation or a continuance over a limited period, the Chargi remarked that in his personal view it seemed most likely that the Soviet Government was thinking of a permanent arrangement. I replied that it would not be an easy matter for us
to grant permission for continuance of the trade mission in Prague, since Ambassador Count Schulenburg had just received from Molotov a not very encouraging pronouncement on the subject of the general state of our relations. The Chargi, in the absence of more definite instructions, interpreted the conversation between Count Schulenburg and Molotov, of which he had knowledge, as meaning that at Moscow they wished to avoid a repetition of the course of events of last January. In Molotov’s view political and economic matters could not be completely separated in our relationship. Between the two as a matter of fact, there was a definite connection.
. . . WEIZSDCKER
The story conitnues with this
The German Ambassador in the Soviet Union (Schulenburg) to the German Foreign Office
No. 113 of June 27
Moscow, June 27, 1939-5:42 p. m.
Received June 27, 1939-8:30 p. m.
Reference your telegram of the 26th No. 132 
As I see it, Mikoyan’s tactics can be interpreted as follows: Mikoyan does not want to see the talks with us broken off, but wishes to keep
 Not printed.
the negotiations firmly in hand, in order to control their progress at any time. Obviously it would not fit very well into the framework of the Soviet Union’s general policy, if a stir should be created by a resumption of the trade negotiations, and above all by repeated journeys of a special plenipotentiary to Moscow. The Soviet Government apparently believes that by resuming the trade negotiations at this particular moment we intend to influence the attitude of England and Poland, and thereby expect to gain certain political advantages. They fear that after gaining these advantages we would again let the negotiations lapse.
. . .
There is, of course, a huge story behind all this. But the point is that the “primary” sources and access to them are critical to the story. Why? In seeking out books on certain inflammatory issues that I wanted to pick up and read, I kept on coming on reviews discounting the books because of their “political leanings.” Whatever the politics. These are books written by experts in their fields as were the reviews, but no matter. The review functions on its own terms, good and bad, the study on another, good or bad. But in my searching I kept on coming back to the notion of the “good stuff.” “The horse’s mouth.” “The source.”
This is an epistemological quandry. If I say, I want to learn about Galileo and thus read a book about Galileo, I will learn about Galileo, sure. But then what? But I could also ask another question. What did Galileo write, and then I could read Dialogue Concerning the Two Cheif World Systems. Then what?
Goodness, I don’t have an answer to your questions, but just checking out “Dialogue” to rea this first sentence made me think both of the people sacrificed to the tsunami and LeGuin’s “The Ones Who Walk Away from Omelas”:
“Though the difference between man and other animals is enormous, yet one might reasonably say that it is little less than the difference among men themselves. What is the ratio of one to a thousand? Yet it is proverbial that one man is worth a thousand where a thousand are of less value than a single one.”
When doing research recently for a history paper I was left in a similar quandry. The topic was slave resistance in America between 1690-1865. Some authors would have you believe that slaves who rebelled suffered from a mental illness called drapetomania. Others would have you believe that every moment of every day every slave was in a constant state of rebellion.
I read more than 25 books on the subject, detecting leanings in each direction. In the end I was left with a wild range of statements and speculation. At that point I turned to the original source documents, letters written by slaves, journals and the WPO slave narratives.
From all of these I was able to bring together my own decisions and thoughts on what happened which to me, lay firmly in the middle of the two main arguments.
Primary source documents themselves can and will have a slant but it is the very existance of that slant that make them valuable.