First, your question is not completely clear. What do the words "prepared to fight Germany" mean? There are three options here:
- Stalin thought that the USSR should be prepared to any war, even with Germany
- Stalin was planning to attack Germany
- Stalin was considering a war with Germany really possible in other scenarios (like German attack)
Point 1, Stalin thought that the USSR should be prepared to any war
This one is trivial, since it's obvious that any normal government should be always prepared for war and there are always numerous documentary evidence of this.
Point 2, Stalin was planning to attack Germany
Regarding this, I can say that there is no such known documentary evidence, but with two important reservations:
to get such documentary evidence, one need either to conquer Russia and take its archives, scour them, and others need to believe him that he hadn't falsified or destroyed anything he found and nothing had been destroyed before him. Or one can "find" a photocopy of such "documents" as was the case with the so-called Secret Protocol of the 1939 Soviet-German Treaty of Non-aggression or the Japanese Tanaka Memorial. So this is not a correct comparison of Russia or Britain/USA or whatever to Germany. Germany was defeated and, most importantly, occupied, so now many documents are widely available, considered genuine and if a document is not available, some witness testimony of its falsification is there (like in the case of the sinking SS Athenia by U-30, when the u-boat's documents were falsified according to a testimony by K. Donitz)
I do not imply to give any corroboration to Suvorov's "findings", which I consider rather foolish
Point 3, Stalin was considering a war with Germany really possible
This is directly related to questions "did Stalin really ignore numerous evidence of German war preparations, intelligence reports about them", was he "mentally broken down" and all this stuff. To address this point one can write a book, so I will give only a couple of instances, which debunk many or at least some of those myths about Stalin and his behavior on the eve of the war.
The most concrete evidence of the fact, that Stalin planned to fight Germany is
the order of military alert (I don't know if this is a correct translation of the Russian term "Приказ о приведении войск в боевую готовность"), which was given on June 18th, 1941 (the order itself most likely was given by Zhukov or Timoshenko, since they were respectively the chief of the General Staff and the People's Commissar (Minister) of Defense at the time, and Stalin had no office in the the Army until July 19th, 1941).
The document itself today may not exist, since it was probably destroyed during the Khrushchev times. Why it was destroyed is another question but this was definitely a part of the anti-Stalin campaign in the USSR during Khrushchev's rule. But there are numerous other documents, which mention that order.
I'll give a citation from the book of a Russian "amateur" historian Yury Mukhin "Great commander in chief J.V. Stalin" with my translation* and my notes in square brackets. Some may consider Mukhin an odious person, but I mention him here only as a tribute to his findings and work, I'll give references to "serious" sources corroborating Muhin's points as well. At least, unlike Suvorov, Mukhin has never been caught with falsification of citations.
But, perhaps, the most mean thing Zhukov did, was that he concealed from historians orders from June 18th, 1941 about military alert state in the western military districts and readiness to repel the German strike. …
Zhukov during Khrushchev's rule destroyed something in the archives of the General Staff, but not everything. Particularly, while Stalin was still alive in the end of 1940s — the first half of the 1950s the Military-scientific directorate (the chief — A.P. Pokrovsky) of the General Staff of the USSR Armed Forces was generalizing the experience of concentration and deployment of troops of the western military districts along with the plan for protection of the state border of 1941 at the eve of the Great patriotic war.
With this purpose participants of those events, who were holding different positions in the military districts at the early period of the war, were asked five questions:
- Were they informed with the plan for protection of the state border, in part, which pertained to their position, when and what was done by the command and staffs to provide the fulfillment of the plan?
- When and along with what order did the cover forces start to deploy at the state border and how many of them had been deployed before the war started?
- When was the order of military alert been received in relation to the anticipated attack of Nazi Germany at morning of June 22nd. What instructions and when were given to fulfill the order and what was done by the troops?
- Why was the major part of artillery placed in training centers?
- To what extent staffs were prepared to command troops and how much did this affect carrying out of first-day war operations?
In 1989 the Military-historical magazine, issue 3, started to publish answers of Soviet generals to this questions, dedicating one article in one issue to answers to one question in turn. It managed to publish answers for the first two question, and as soon as the turn came to question 3, "When was the order of military alert received?" — the publication ceased without any explanation from the magazine. Gareevs and anfilovs [Makhmut Gareev and Viktor Anfilov are "professional" historians, Gareev himself is the president of the Russian Academy of Military Sciences] suddenly checked themselves. But even from what had been published by the magazine, it became evident that in the Baltic military district this order was received long before the full-scale war.
These accounts of the generals can be checked in issue 3 of the magazine a pdf-file in Russian, p. 68 of the file and issue 5 p. 25. I cannot provide them here, since it would increase the size of the already long answer even more, but the fact is, that the German attack was not a surprise for neither the USSR, nor Stalin.
The notion about the "surprise attack" was concocted during the anti-Stalin libel campaign. For Zhukov and his fellows one probable reason to do this, was to explain some how great defeats the Red Army suffered at the early stage of the war and to cover their own failures.
There is also a myth at least in Russian historiography, that in the Navy, heroic people's commissar of the Navy Kuznetsov without Stalin's decision/permission gave the military alert order to the Navy. I'll once again give a citation from Mukhin's book "Great commander in chief Stalin":
… such an order [for military alert] was given on June 18th. This is corroborated by specially collected memoirs of survived generals of those days and their reports about execution of that order. During Khrushchev and Zhukov all this was distorted, memoirs were written accordingly: let's say, people's commissar of the Navy Kuztensov states that he secretly from Stalin and Timoshenko put the Navy into the military alert state. This is ridiculous in and of itself, but the important part is, that there is a report of commander of the Baltic fleet Tributs, where he informs about the fulfillment of the order not Kuztetsov, but the commanders of the the Baltic and Leningrad military districts, those from whom he received the order.
I hope, I was able to give a corroborated explanation about the fact that the USSR and Stalin were definitely in full awareness of the anticipated war and planned to fight Germany and reasons for the defeats of the early period of the war lie elsewhere, not in the "fact" that Stalin was stupid and "believed" that Hitler would never attack. Not to mention all these Khrushchev-Mikoyan lies about Stalin being afraid of Beria to arrest him in 1941 etc.
* If anyone needs a direct reference to the citation, one can search the book "Великий главнокомандующий И.В. Сталин" for the words "пожалуй, наибольшей подлостью Г.К. Жукова явилось", I cannot provide a page number, since I have an e-book edition.