The all-Ireland census was conducted on 30 March 1851, during the famine's late phase. It counted 6,552,385 people on the island, against 8,175,124 in 1841 — a recorded decline of 1,622,739, or 19.85 percent.
That number is not a death toll. Census totals measure net population change, so the gap combines mortality, emigration, births and possible enumeration error.
Leaving, at the peak
Transatlantic emigration reached its famine-era peak during 1851, when just under a quarter of a million people left Ireland.
Better harvests after 1849 had eased pressure across much of the island, but localized blight and famine conditions continued in southwestern districts through 1852. Poor Law unions went on supporting destitute people while the worst-hit western and southwestern districts stayed under strain.
The volumes, and the fire
The Ireland Census Office recorded the demographic consequences visible by 1851. The volumes examining famine disease and mortality were prepared in part by the physician and census commissioner William Wilde.
1851 was neither the beginning nor the worst year of the famine; the heaviest mortality came earlier, especially during Black '47. What the year supplies is the measurement rather than a new calamity.
Most individual returns from the census that measured the catastrophe were destroyed in the 1922 Public Record Office fire.
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What the sources leave uncertain
The source listing supplies only the year 1851, although the census anchor used here has the independently verified date March 30.
Census totals measure net population change, not deaths. The difference between 1841 and 1851 combines mortality, emigration, births, and possible enumeration error.
Pre-famine population estimates can exceed the official 1841 count because the population continued growing before the blight and because historians question census completeness.
The Gesta Francorum places the beginning of the main attack on Wednesday and Thursday, 13 and 14 July 1099, saying the crusaders attacked Jerusalem from every side by night and by day.
This time they had equipment. The siege towers and other machinery built over the preceding weeks were in use: Godfrey of Bouillon commanded the principal northern tower, Raymond of Toulouse the southern operation.
Why they could not wait
The machinery was finished, and news had come that a Fatimid relief army was approaching from Egypt. A prolonged blockade was no longer affordable.
Raymond of Aguilers reports about 12,000 fighting men, including 1,200 to 1,300 knights. Jonathan Riley-Smith calls the resulting estimates credible but still guesses.
No foothold, and no retreat
No decisive foothold was secured on 13 July. The assault was not abandoned either — fighting and efforts to move the towers against the walls continued through 14 July and into the 15th.
The northern tower still had to be brought across a filled ditch and close enough for its timbers to serve as a bridge.
On 15 July Godfrey's tower reached the northern wall, crusaders crossed onto it, and the city's defense collapsed.
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What the sources leave uncertain
The date is secure in the contemporary weekday sequence: Wednesday was 13 July and Thursday was 14 July.
Modern narratives variously say the final assault began on the night of 13 July or at dawn on 14 July. The Gesta encompasses both Wednesday and Thursday and describes continuous night-and-day fighting.
The figure of 12,000 is a contemporary estimate transmitted by Raymond of Aguilers, not a modern head count.
At about 10 a.m. on 14 December 1812, Russian forces under Matvei Platov and Joseph O'Rourke reached Kovno, still held by Marshal Michel Ney's French rearguard.
Cossacks crossed the frozen Neman above and below the town and threatened to surround the defenders. Ney evacuated Kovno that evening, burning the bridges over the Neman and the Vilija as his force withdrew.
What was left of the central army
The organized remnant representing Napoleon's central army that day amounted to roughly 1,000 combatants — 400 Old Guard infantry and 600 Guard cavalry — with nine guns before the losses at Kovno.
Russian forces took about 3,000 prisoners, four guns and substantial stores when the town fell. Ney fought through Kovno and got away with only about 200 armed men still around him.
Why this is not quite the end of the invasion
The evacuation removed the last organized rearguard of the central army across the Neman, but Macdonald's northern corps and the Schwarzenberg–Reynier wing were still on Russian territory, so the claim that all remnants were expelled on 14 December is inaccurate.
Sources also disagree on the day itself. The detailed Kovno narrative dates Ney's evacuation to 14 December; other accounts, among them the EHNE encyclopedia, put the survivors' crossing of the Neman on 13 December, and one Fondation Napoléon overview gives 16 December. The Gregorian 14 December corresponds to 2 December in the Russian Julian calendar then in use.
The often-repeated image of Ney firing the last shot and being the final Frenchman across comes from memoir tradition rather than an uncontested official record.
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Date disputed. Sources disagree about when this happened.
What the sources leave uncertain
December 14 is Gregorian and corresponds to December 2 in the contemporary Russian Julian calendar.
The standard Kovno narrative dates Ney’s evacuation to December 14, but one Fondation Napoléon overview dates the re-crossing to December 16.
The larger claim that the invasion itself ended because all remnants were expelled on December 14 is inaccurate: contemporary campaign histories explicitly note that Macdonald’s northern corps and the Schwarzenberg–Reynier wing were still on Russian territory.
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