Russian troops in bivouac, note the soldiers sleeping in their greatcoats and the only tents pitched are to protect the muskets from damp.
Kankrin's estimate of the amount of supplies that can be requisitioned in the local area of a Corps for 1-2 days can be combined with Clausewitz's estimation to produced a working model based on a supply area of a 2 Meile square (15 km). However Clausewitz does state that:
"Still, we must remember that if the breadth of the front of a column is extended from two miles to three, we get a superficial extent of country more than double in size, that is, instead of four we command nine square miles, and that this is still an extent which in ordinary cases will always admit of concentration for action;"
Later in the same chapter:
"Of course this is a mere rough estimate of what may take place, subject to many modifying circumstances which may intervene, of which the principal is, that one district may not be capable of contributing like another. But on the other hand, we must also remember that the radius within which we can levy may increase more than two miles a day in width, perhaps three or four, or in many places still more."
This fits in well with Kankrin's statement that in an area of 1500 inhabitants per Q Meile (26 inhabitants per km sq) it is just possible to subsist without support from magazines. The troops would just have to be quartered over a slightly larger area.
Given this, the table can be modified into three columns, showing 'normal' operations (15 km) 'extended' operations (22 km) and finally a wide area used when the enemy is some distance away (30 km). In the case of the second and third columns, a lower multiplier of x3 is used rather than Clausewitz's x4 to account for a lower efficiency of the corps being spread over a wider area.
| Number of troops sustained by certain levels of population density – Combination of Clausewitz and Kerstin methodology | ||||
| Population density inhabitants per Q Meile (per km2) | Foraging square of 2 Q Meile (15 km) | Foraging square of 3 Q Meile (22 km) | Foraging square of 4 Q Meile (30 km) | |
| Area | 4 QM or 225 km2 | 9 QM or 500 km2 | 16 QM or 900 km2 | |
| Clausewitz multiplier | x4 | x3 | x3 | |
| Highly cultivated | 3000 (55) | 48,000 | 81,000 | 144,000 |
| Highly cultivated | 2000 (35) | 32,000 | 54,000 | 96,000 |
| Medium cultivated | 1500 (27) | 24,000 | 40,500 | 72,000 |
| Medium cultivated | 1000 (18) | 16,000 | 27,000 | 48,000 |
| Little cultivated | 800 (14) | 12,800 | 21,600 | 38,400 |
| Semi-desert | 300 (5) | 4,800 | 8,100 | 14,400 |
| Desert | 150 (3) | 2,400 | 4,050 | 7,200 |
| Requisition from local area and quartering | ||||
| Mix of requisition, quartering with the aid of magazines | ||||
| Magazines and supply transport required to sustain armies | ||||
| Unsuitable for large armies | ||||
| Short distances for small corps can find the means. | ||||
This table is revealing in several ways. Applying it to the Napoleonic Wars it shows that both Spain (18 inhabitants per km sq) and Russia (14 inh/km sq) could support armies by requisitioning but that this was only just possible, in the case of Spain, once the guerrillas denied access to the wider countryside, French armies had to rely on magazine supply and in Russia, once an army had passed through a region (the French army was particularly destructive,) it could not support another one that season. Likewise it shows that the Allied armies operating in Germany during 1813-14 could maintain themselves in Prussia, Saxony and Bohemia so long as they kept moving but that once stopped they would need additional support, which is exactly what happened during the Armistice of 1813.
Furthermore, the issue of what happens when the army stops moving is covered by Clausewitz who gives two options, firstly living for eight days from the rations carried by the men in their knapsacks and the stores in the accompanying regimental wagon train or secondly by using the Commissariat to requisition supplies from a wider area using the local magistrates to administer this and local farmers wagons to transport the supplies to the camp.
This applies to all the Corps which make up the army, both authors envisage an advance of three Corps spread out over a frontage of 6 or 9 Meile (45 km or 68 km) with a second echelon of Corps following along a days march behind. This allows an army of 150,000 men to march across countryside of 35 inhabitants per km sq by quartering or local requisition or countryside of 18 inhabitants per km sq by a mix of requisition and some supplies delivered from magazines or wider requisitioning.
Similarly the table can be used to examine the 17th, 18th and 19th centuries operations by adding a table of population density and being aware of a number of caveats. There was a marked increase in the efficiency of road transport due to hardening of roads and improved vehicle design, which in Britain took place from 1660 to 1760 and there was a steady agricultural revolution from the 17th century onwards, particularly in the Netherlands and Great Britain, so that fewer inhabitants could grow more food. This led in turn to a growth in population but also an increase in urbanisation. For the 19th century, the growth of railways from the 1830s, meant that it was now possible to move bulk food stocks around at a low cost, which contributed to further urbanisation. Since the Clausewitz/Kankrin model uses population density as a measure food stocks, the 17th and first half of the 18th centuries will overstate the available food because agriculture is less efficient, while the railways allowed substantial populations to arise which import their food from outside their region. However for many regions these factors would not change the basic fundamentals until after 1945.
| Population Density calculated from Maddison | |||||
| numbers of inhabitants per km2 | |||||
| 1600 | 1700 | 1820 | 1850 | 1900 | |
| Great Britain | 20 | 28 | 68 | 87 | 132 |
| Netherlands | 20 | 25 | 31 | 41 | 68 |
| Belgium | 52 | 66 | 112 | 146 | 220 |
| France | 39 | 46 | 66 | 77 | 86 |
| Spain | 16 | 18 | 24 | 30 | 37 |
| Portugal | 12 | 22 | 36 | 41 | 59 |
| Italy | 44 | 45 | 68 | 83 | 114 |
| Switzerland | 24 | 29 | 48 | 84 | 80 |
| Germany | 22 | 21 | 35 | 47 | 76 |
| Poland | 16 | 19 | 32 | 40 | 77 |
| Austria | 30 | 30 | 40 | 47 | 71 |
| Bohemia & Moravia | 60 | 60 | 103 | 124 | 163 |
| Hungary | 13 | 16 | 45 | 55 | 77 |
| Russia | 5 | 7 | 14 | 19 | 31 |
| Europe | 19 | 21 | 35 | 44 | 62 |
| United States | 7.9 | ||||
| Confederacy | 4.6 | ||||
| Density over 35 = Corps able to support itself from local area | |||||
As the table shows armies prior to the Napoleonic Wars had to contend with lower population densities and available food supplies and there were only a few areas in Europe that could support armies by local requisitioning throughout the period such as the Low Countries, France, Northern Italy and Bohemia/Moravia. Prior to the introduction of Corps d'armee in 1800, armies moved as concentrated forces, often much larger than a Corps of 30,000 men. This limited the capability of the local area to support the armies, for instance Frederick the Great in the Seven Years War fielded a main army in the region of 50,000 men, operating in Silesia and Saxony (31 inhabitants per km sq in 1740) which could support forces up to 30,000 men. The tight control of the infantry in regular tented camps with limited opportunities for foraging, left the cavalry as the principal foragers, mainly for fodder or in raising monetary contributions from local towns. This dictated the need for a large amount of supply to come from magazines and the integration of marching patterns with the movements of the field bakery and the setting up of formal, often entrenched camps.
In the period after the Napoleonic Wars, on one hand supply became easier because the local area had increased resources but this was balanced by an increasing demand from the troops as ration standards increased, the standard of care for the sick and wounded rose with the introduction of ambulances and the beginnings of an inexorable rise in additional equipment, from field telegraphs to machine guns with all the additional horses that entailed. In Europe some sort of balance was struck up to the final decade of the century when the increasing size of armies to millions of men, larger corps such as the German Army Corps of 1914 with 48,000 men and the increased equipment establishment started to exceed the ability of even the sophisticated agricultural produce supply chains of northern Europe.
Interestingly, the one large scale and long term war to be fought between the Napoleonic Wars and the Great War, was conducted in an area of very low population density, the United States of America where the average was only 8 inhabitants per km sq and in the Southern States 4.6, which in the early war years was an overstatement since the principal crop grown was cotton for export. Basing their experience on Napoleonic standards, American staff officers struggled to get a balance between mobility and supply even though they fully utilised railways both to move troops and supply them. Different solutions to this problem was found by the Army of the Potomac, the Union Western armies and the Confederate Army.