General Chasseloup-Laubat (1754–1833). The celebrated engineer who directed French operations at Danzig, Kolberg and Stralsund. At Danzig he was opposed by fellow Frenchman, Bousmard, an engineer whose methods he had studied and absorbed.
The Siege of Danzig. A French map of the siege, indicating the siting of French batteries. Please note the left-hand side of the map is north.
An 800-year-old port at the mouth of the Vistula, Danzig is of major strategical importance. A fortified city of great wealth, crammed with bursting storehouses and magazines, it is a bastion on the Baltic: constituting, in Napoleon’s mind – as Petre notes – ‘a standing menace, whilst in the enemy’s hands.’ In fact, Napoleon is obsessed with Danzig, considering its capture vital for a variety of reasons: first, to deny the port’s facilities to the Russians, who – with the help of the British Royal Navy – might attempt a landing in his rear; second, to remove the threat posed to his left flank by the Prussian garrison; third, to exploit the city’s great strategical and material resources himself. And last – but perhaps not least – to divert attention away from his failure to crush Bennigsen at Eylau. Thus, as Petre states: ‘Scarcely was the battlefield of Eylau cleared when, on 18 February, Napoleon commenced his arrangements for the siege, which had been interrupted by Bennigsen’s advance, necessitating the recall of Lefebvre to guard Thorn.’
Marshal François-Joseph Lefebvre – former commander of the infantry of Napoleon’s Old Guard – is, according to Foord, ‘merely a rough, honest old soldier of little strategic or tactical ability.’ Of humble background (his father was a miller), this tough 52-year-old veteran is a replacement for the unfortunate General Claude Victor, captured while changing horses near Stettin by a party of Prussian soldiers disguised as peasants. Lefebvre knows nothing of siege warfare, but will be aided in his task by Napoleon’s top engineer, General Chasseloup-Laubat. As for Lefebvre’s command, it consists of the 26,000 troops of X Corps. Only some 10,000 of these soldiers are French, the rest being an assortment of foreigners, largely Poles and Saxons. But Lefebvre’s force will continue to grow over the coming months, strengthened by a steady stream of captured Prussian ordnance from the fallen fortresses of Silesia.
Opposing X Corps is a complement of some 16,000 men, augmented by 450 guns, howitzers and mortars. The bulk of the manpower – around 11,000 men and 300 guns – is concentrated in Danzig itself, the remainder strung out in detachments north of the city, tasked with maintaining communications with the Baltic. Despite later claims (from both sides), these garrison troops are not of the first class: but they are well-supplied and ably led by General Count Friedrich Adolf von Kalkreuth (also spelt ‘Kalreuth’, ‘Kalckreuth’ or ‘Kalkruth’ in contemporary sources), a veteran of the Seven Years War. Like Lefebvre, Kalkreuth is no expert when it comes to sieges, and will rely, in his turn, on an experienced advisor. But this guru is none other than the celebrated French émigré, Henri Jean-Baptiste Bousmard, whose treatise on the science of siege warfare, General Essay on Fortification (published in the 1790s and dedicated to the king of Prussia) is Chasseloup’s bible. Thus, the commanding generals will preside over a game of cat-and-mouse between the 58-year-old Bousmard and the 53-year-old Chasseloup: two clever and resourceful men, seemingly sharing the same textbook. But the game will be a lethal one, and only one of the two Frenchmen will survive.
The venue for the Bousmard v. Chasseloup match is a walled city protected by nineteen bastions. Danzig – an old Hanseatic town – was bagged by Prussia in 1793 during the Second Partition of Poland. The city’s inhabitants – Germans and Poles – had enjoyed hundreds of years of municipal autonomy: consequently, Prussian rule was despised. In 1797 a rebellion broke out but was soon crushed, Danzig remaining in Prussian hands.
In 1807, as Petre states: ‘the civil population of Danzig numbered about 45,000. The city had somewhat declined in importance of late years, yet was still a very important port and market. Its fortifications had, in 1806, been much neglected, and were in very bad repair. It was only when the Prussian power collapsed, in the autumn of that year, that a siege began to seem probable. Then every effort was made to repair and strengthen the fortress.’
In fact, Danzig’s fortifications are formidable, its storehouses full, and its approaches covered by boggy ground and several waterways. It will be a difficult nut for Chasseloup to crack. Above the city, the Vistula – flowing from east to west – hugs the northern flank of the fortress. Then, once past Danzig, the river sweeps north in a wide arc, through a vast swampy plain, known as the Nehrung, before emptying into the Baltic a few miles beyond. The navigable Laake Canal cuts through the eastern Nehrung, connecting Danzig with the estuary, thus creating the garrisoned island of Holm, the southern tip of which gazes across the Vistula at Danzig’s northern walls. The mouth of the Vistula is guarded by a small fort at Weichselmunde, opposite the tiny port of Neufahrwasser. Meanwhile, to the east and south of Danzig lies more marshland, intersected by several streams, including the River Mottlau: a tributary of the Vistula, which, running through the centre of the city, bisects it on a north–south axis. To the west – the only practicable line of attack for a hostile army – stand the fortified bastions of the Hagelsberg and the Bischofsberg (armed with forty guns apiece): the first dominating the main approaches to the city; the second forming its south-west corner.
Dabrowski’s victory at Dirschau on 23 February has effectively confined Kalkreuth’s troops to the precincts of Danzig, leaving Lefebvre free to make his advance on 9 March. The next day, having driven in the Prussian outposts, the marshal occupies villages south and south-west of the city. Several days later, the western suburb of Schidlitz is successfully stormed.
But Napoleon wants Danzig’s communications with Weichselmunde and the Baltic cut and orders Lefebvre to encircle the city. Consequently, on 20 March, General Jean-Adam Schramm – operating on Danzig’s eastern flank – leads 2,000 French troops onto the northern bank of the Vistula, and marches west on Weichselmunde. The small French task force succeeds in pushing the Prussian outposts back along the eastern Nehrung and into the fortress of Weichselmunde itself. Speedily reinforced by Lefebvre, Schramm then beats off a sortie from Danzig, and secures a position on the Nehrung north of Danzig: his right anchored on the Baltic, his left on the Vistula. The French stranglehold on the port is tightening. Now Lefebvre feels himself strong enough to open a regular siege.
By 1807 the basic method for beleaguering a city is well-established. The engineers on both sides know what to expect. First, the attackers will attempt to isolate the garrison by enforcing a blockade. Then, at a safe distance, an initial trench or ‘first parallel’ will be dug opposite a section of the city walls. Once completed, saps will advance from this trench until a ‘second parallel’ is completed, and then a third, and so on, until the walls are almost reached. Meanwhile, well-sited batteries will batter the walls facing the trenches, and when a breach is made, the city will be invited to surrender. If the invitation is refused, the attackers will issue from the trenches and storm the breach. Should the fortress fall, a time-honoured tradition – dating back to the Middle Ages – grants victors the ‘right’ to murder the garrison and plunder the town as ‘punishment’ for obliging them to suffer casualties by mounting an assault. So much for the theory.