84 Wallenstein
far between as well as easily fortified or broken down. Hence over the
winter Wallenstein had substantial defences constructed on both sides
of the Elbe bridge at Dessau, 30 miles south-east of Magdeburg, and
he placed Aldringer there with a garrison to defend it. Magdeburg and
its bridge were in Protestant hands, while south of Dessau all the way
to the Bohemian border the Elbe flowed through Protestant Saxony,
so that securing the bridge was a prudent precaution as well as prevent-
ing the river being used as a supply line by the enemy. Nevertheless it
was a surprise when in April 1626, after taking the town of Zerbst nine
miles to the north-west, Mansfeld mounted an attack on the defences
around the northern end of the bridge.
Despite the confident accounts given in many histories it is very diffi-
cult to describe accurately what happened at battles in the early modern
period. Numbers are the first problem. Contemporary reports give large,
round and probably exaggerated figures, and for want of anything bet-
ter these often pass from one history to the next, eventually becoming
accepted as though they were established fact. The starting point in the
Thirty Years War was to list the units involved, which were known by
the names of their commanders and were usually well recorded, and to
tot up their nominal strength, 3000 for an infantry regiment, 300 for
a company, and 1000 and 100 for the equivalent cavalry formations.
The result was the maximum figure, although the one often reported,
but units were rarely at full strength even in total, while after deducting
the sick, wounded, missing and dead the numbers available and fit to
fight could be very much lower, sometimes half or less. This may not
matter, as the same applied on both sides, so that the relative strengths
quoted may be somewhere near right even if the absolute numbers are
wrong, but it helps to explain the frequent discrepancies between dif-
ferent reports of the same event. Numbers of casualties were even more
arbitrary, as the dead were mostly buried in mass graves and perhaps
not even counted, while those who failed to return for roll-call and
were not known to be prisoners were simply struck off the company
lists, so that there was no distinction between casualties and deserters.
Prisoners were no better accounted for, usually simply being enrolled
by the winning side, and here too the numbers represent the loosest of
estimates or perhaps simply guesswork. The most accurate figures after
a battle seem to have been the number of enemy standards taken –
a particular point of military pride – and perhaps the number of cannon
captured.
The course of a battle is often as unclear as the numbers involved. Two
hundred years later the duke of Wellington noted ‘how little reliance