The Battle of Britain Five Months That Changed History, May—October 1940 by James Holland (z-lib.org).epub

corridor in which the BEF and French First Army were now trapped,
capturing the low heights around the town of Cassel, then heading straight
to Courtrai and linking up with Army Group B – and, in so doing, cutting
off the British retreat to Dunkirk still some thirty miles to the north-west.
Fully armed, highly confident panzers, a-brimming with supplies and
ammunition against infantry low on rounds and increasingly hungry would
have been no contest at all. The BEF would have been annihilated.
Even more galling was that for a number of units who had already made
it across the Canal Line, the order was not a halt but, rather, a retreat, as
they had to pull back across the water. Early on the 25th, Guderian visited
the Waffen-SS Leibstandarte Division and found them crossing the River
Aa in defiance of the order. Guderian crossed too and eventually found the
commander, Obergruppenführer Sepp Dietrich, in the ruins of a castle on a
well-placed hillock called Mount Watten. When Guderian asked him why
he was disobeying orders, Dietrich pointed out that Mount Watten
commanded a very strong position and that the task of crossing the Aa
would be very much harder if it was in enemy hands. Guderian not only
approved Dietrich’s action, but ordered some of 2nd Panzer to move up in
support.
Von Brauchitsch had been summoned to see Hitler on the afternoon of
the 24th. It had been his chance to point out both the lunacy of the measure,
and the golden opportunity now before them to finish off the battle in the
north with the destruction of the BEF. When he arrived back at the OKH
command post at 8 p.m., Halder found him shaken and humiliated; far from
convincing Hitler, von Brauchitsch had been forced to listen to one of the
Führer’s furious rants. The Commander-in-Chief tried to put across his
arguments, but failed. ‘Apparently again a very unpleasant interview with
the Führer,’ noted Halder tersely.
However, while von Brauchitsch had been receiving his tongue-lashing
from Hitler for daring to act independently, Halder had been working out
how to get around the halt order. Late in the afternoon he had come up with
a cunning plan and accordingly issued a message to Army Groups A and B.
‘Expanding on the directives in the May 24 Army High Command order’ he
gave the ‘go-ahead’ for the continuation of the attack towards Dunkirk–
Cassel–Estaires–Armentières–Ypres–Ostend – in other words, not the entire
Canal Line, but just the northern half, which would shut the gate on the
retreating British. This was clever wording; a ‘go-ahead’ was not the same