General Heinz Guderian had been the principal German theorist of the style of tank led warfare that was to become known as ‘Blitzkrieg’. Now he commanded Panzergruppe 2 and would play a leading role in the rapid advance into Russia, he was already known as “Hurrying Heinz” because of his impatience to press on with his armoured columns:
On the 20th and 21st I visited the forward units of my corps to make sure that all preparations for the attack were satisfactorily completed. Detailed study of the behaviour of the Russians convinced me that they knew nothing of our intentions. We had observation of the courtyard of Brest-Litovsk citadel and could see them drilling by platoons to the music of a military band.
The strong points along their bank of the Bug were unoccupied. They had made scarcely any noticeable progress in strengthening their fortified positions during the past few weeks.
So the prospects of our attack achieving surprise were good and the question therefore arose whether the one hour’s artillery preparation which had been planned was now necessary after all. I finally decided not to cancel it; this was simply a precaution lest unexpected Russian counter-measures cause us avoidable casualties.