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

As at the Meuse, getting safely across a key water feature was the key to an
operation; so as far as the buoyant Germans were concerned, the path to
Dunkirk was now well and truly open, particularly since the bulk of the
BEF was still south-east of the port. Calais and Boulogne had already been
isolated and were expected to fall any moment, so it seemed to Guderian
that the BEF and French First Army were now completely trapped with
nowhere left to run.
Then, at 12.45 p.m., Guderian received an urgent order, from the Führer
no less. North-west of Arras, all German forces were to halt along the line
Lens–Béthune–Aire–St Omer–Gravelines. In other words, along the Canal
Line. Hitler wanted ‘all mobile units to close up’. First Panzer wasn’t the
only unit to have already won bridgeheads across the Canal Line. So, too,
had the SS-Totenkopf Division at Béthune, for example. ‘We were utterly
speechless,’ wrote Guderian. ‘But since were not informed of the reasons
for this order, it was difficult to argue against it.’
In fact, the origins of this fateful order could be found the previous day,
when von Kleist had told Army Group A and OKH that his units were now
quite widely spread, conducting attacks along the Canal Line and the
Channel ports, and protecting their own southern flank. He told von
Rundstedt that his panzer strength was down to 50 per cent, which was
actually a far more pessimistic assessment than was the reality. He thus
warned that if the enemy counter-attacked in strength then he believed his
lead divisions might have some difficulties. However, there was no sign of
any major counter-attack and nothing about the performance of the French
or British suggested one was imminent.
Nonetheless, General Günther von Kluge was alarmed by von Kleist’s
message. Although commander of the Fourth Army, which included
Rommel’s 7th Panzer and Panzer Corps Hoth pressing north from Arras, he
had also been given overall command of all the mobile forces on his left –
i.e. all of Panzer Group Kleist. At 4.40 p.m. on the 23rd, he spoke to von
Rundstedt and suggested a close-up order be issued, halting the fast-moving
mobile forces while the infantry divisions such as 87th Division, of which
Leutnant Siegfried Knappe was a part, caught up.
This was the same old concern that had repeatedly reared its head ever
since the plans for the offensive had first been drawn up; and it represented
the same doctrinal differences between the old-school conservatives and the
progressives such as Guderian, Halder, Reinhardt and Rommel. Von