The XIX Army Corps became part of the German effort to trap the Allied troops with an attack through the Ardennes forest, devised by Erich von Manstein known as the sickle cut.

[15] Initially, the attack was planned to be launched on 26 August 1939, but in the night before the assault was to commence, the operation was abruptly cancelled due to diplomatic developments, causing a brief uncertainty whether the military campaign would take place at all.

[22] The Army Corps saw its first notable engagement with the enemy north of Sępólno Krajeńskie when the German panzers were surprised by the sudden dissipation of the fog and subsequently found themselves opposite Polish anti-tank units.

[22] On 2 September, the German forces gained a river crossing northeast of Chojnice, threatening to encircle the city and prompting Polish counter-attacks (see also Battle of Tuchola Forest).

[b] American writer and journalist William L. Shirer visited the site of the skirmishes between the Pomorska Brigade and XIX Army Corps a few days later, describing it as "sickening evidence of the carnage" and "symbolic of the brief Polish campaign".

[23] By 5 September, XIX Army Corps had broken the enemy resistance and thwarted the attempts of the Polish 9th Infantry Division and the Czersk Operational Group to recapture the Brda's east bank and force the Germans back across the river.

[20][24] Küchler's forces had their main strength concentrated in the Nidzica-Wielbark area and had been met with fierce resistance by well-entrenched Polish defenders of the Modlin Army who benefitted from the swamps and forests north of Mława and Przasnysz.

Once more, Von Bock instructed Guderian to set his sights onto Brest-Litvosk, far east of the line between Ostrów and Warsaw previously given by OKH and deep in the Polish rear.

Miscommunications with the infantry-based XXI Army Corps during their Narew crossing caused casualties; German infantry units, if unsupported by armored or air forces, had great trouble overcoming well-entrenched Polish defenders.

The remains of the battered Polish Narew Operational Groups, supported by the Podlaska Cavalry Brigade, were now in XIX Army Corps' left rear, in the Grodno and Białystok areas.

Plisowski's Polish soldiers, just like Raginis' units at Wizna, slowed down XIX Army Corps in spite of the crushing numerical and technological advantages on the German side.

For future developments it should be kept in mind that speed was sufficient, but that it was important to strengthen the armor, especially in the front, and to increase the range and piercing of the guns, thus larger barrels and projectiles with bigger loads.

XIX Army Corps was part of the effort to trap the Allied troops with a strong attack through the Ardennes forest, a plan devised by Erich von Manstein with consultation from Guderian in November 1939.

[34][35][36][37] One day in November, [Erich von] Manstein asked me to see him and offered his thoughts on a strong panzer attack through Luxembourg and southern Belgium against the extended Maginot Line at Sedan, to pierce that fortified front and to then complete the breakthrough through the French frontline.

[35] In a secret command document of 7 November 1944, the German inspector-general of panzer forces is given the following recapitulation of the preparations for Case Yellow:[38] Guderian and the staff of XIX Army Corps was called into position at their initial headquarters at Bitburg on 9 May 1940 at 13:30.

[39] Karl-Heinz Frieser identifies the Sedan sector under X Corps (Pierre-Paul-Jacques Grandsard) on the left flank of the French 2nd Army as the weakest part of the defensive line.

[32][44] Throughout the campaign towards the Meuse, XIX Army Corps was heavily supported by the German Third Air Fleet, which struck at French troop movements, infrastructure, railroad and rear guard communications at an exceptional operational depth of on average 76 kilometers per sortie.

At this point, XIX Army Corps had become a prime target for Allied bombardment, as its crossing of the Meuse river would establish a deadly bridgehead for German reinforcements to quickly overrun the Belgian defenses.

[42][32] On the evening of 12 May, yet another Korpsbefehl was given out, informing the officers that Luftwaffe capacities had been freed up over Belgian airspace and would be used to support Panzer Group Kleist in the hugely important Meuse crossing the following day, 13 May 1940.

[52] On the 14th, the bulk of the heavy detachments of XIX Army Corps began crossing the Meuse river under the cover of the infantry and recon units holding the bridgeheads.

The directive warned the officers that most Somme crossings and bridges were in Allied hands and thus instructed a swift series of surprise attacks to quickly break the resistance at the bridgeheads.

[63] The Somme had large symbolic significance due to its importance during World War One, but the capture of Péronne also meant that the route towards Amiens in the south and Arras in the north and thus the last major French settlements (next to Abbeville) between the German lines and the English channel was now open.

[71] By the evening, Guderian had instructed 1st Panzer Division to switch its main target from Calais to Dunkirk and to await a coded messages to begin the assault the following day.

[80] He does not mention misbehaviour by Leibstandarte troops on any other occasion either and generally fails to properly acknowledge and work through German war crimes during any of the three theaters his book covers (Invasion of Poland, Battle of France and the Eastern Front) and has been criticized by British historian Ian Kershaw, among others, for trying to reflect himself in the best possible light.

By now, French tactics against armored units had changed - open fields were only rarely defended against the panzers, whereas settlements and forests became nests of resistance against German infantry advances.

[96] Halder noted in his entry of 10 June 1940 that Group Guderian managed to reach Joinville ahead of schedule, leading the spearhead east of the river Oise.

[96] On the following day, a strategically valuable bridge was captured in an undamaged state by 1st Panzer Division at Beaujeu-Saint-Vallier-Pierrejux-et-Quitteur, north of Gray, enabling the Germans to cross the Saône river.

During the river crossing, German pilots identified by Guderian as belonging to Wilhelm Ritter von Leeb's Army Group C.[101] Although the ground forces were delayed by the fact that they had to seek cover from the friendly fire, they suffered no casualties.

[96] On 17 June, 29th Infantry Division was among the first German units to reach the border to Switzerland, meaning that any remaining Allied soldiers on the Maginot Line were now threatened to get completely cut off.

Guderian planned to have the troops advance into the Vosges region on a wide front, but was met with infrastructural issues when large amounts of German infantrymen of I Army Corps also entered the operational area.