Xerxes' pontoon bridges
Most modern historians accept the building of the bridges as such, but practically all details related by Herodotus are subject to doubt and discussion.
Herodotus relates in his Histories that the Second Persian invasion of Greece already intended by Darius I was carefully prepared by his son Xerxes I.
Among many other things he also ordered ships of war to be furnished and ropes of papyrus and of white flax to be prepared for the bridges.
He is then said to have thrown fetters into the strait, given it three hundred whiplashes, and branded it with red-hot irons as the soldiers shouted at the water.
When a part of the Persian army later retreated to the Hellespont, they only found the debris of the bridges destroyed by another storm.
[10] Herodotus' narrative should, perhaps, not be taken as a bridge engineer's sober technical report but rather as a vivid illustration of the grandeur of the Persian king which would make the Greek victories appear even more outstanding.
[11] Details in the play The Persians by Aeschylus (an Athenian playwright) written in 472 BC, less than a decade after the bridge is said to have been built, tend to corroborate the idea of it.
[clarification needed] In that play, Atossa, the mother of Xerxes, learns of what a disaster her son's invasion of Greece has been.
With the lightning's speed Jove on my son hath hurled his threaten'd vengeance: Yet I implored the gods that it might fall In time's late process: but when rashness drives Impetuous on, the scourge of Heaven upraised Lashes the Fury forward; hence these ills Pour headlong on my friends.
Not weighing this, My son, with all the fiery pride of youth, Hath quickened their arrival, while he hoped To bind the sacred Hellespont, to hold The raging Bosphorus, like a slave, in chains, And dared the advent'rous passage, bridging firm With links of solid iron his wondrous way, To lead his numerous host; and swell'd with thoughts Presumptuous, deem'd, vain mortal!
[citation needed] Aeschylus was an Athenian playwright who had fought in the battle of Salamis, and witnessed there the destruction of the Persian fleet.
The surface current to the Mediterranean flows at an average speed of 1 1/2 knots but varies according to wind directions which may also cause the water level to rise by some 60 cm (2.0 ft).
[12] At present, the narrowest part of the Dardanelles between Çanakkale and Kilitbahir (40°8′38.32″N 26°23′23.45″E / 40.1439778°N 26.3898472°E / 40.1439778; 26.3898472) is about 1.4 km (1,530 yards) wide and has a maximum depth of 91 m (299 ft).
[14] Çanakkale was built during the early Ottoman Empire on the alluvial gravel fan deposited by a river, in winter often a torrent,[15] descending from the nearby mountains (and recently tamed by the Atikhisar dam).
Abydos, the town mentioned by Herodotus, was north of Çanakkale on the Asiatic shore near Nara Burnu (formerly Nagara) (40°11′47″N 26°24′52″E / 40.19639°N 26.41444°E / 40.19639; 26.41444).
The British Major-General Frederick Barton Maurice, on a visit to the area in 1922, considered a beach further north to be the only acceptable location for a bridge from a military point of view; but there, the distance across is more than 3 km (3,280 yards).
The lowest oar ports of a trireme were about 30 cm above the waterline and were normally fitted with leather sleeves,[18] an aspect which does not really qualify them as a bridge carrier.
Pontoon bridges across rivers are usually held in position by anchors fastened to the bow and stern of each boat[19] and thus, at a first glance, Herodotus' description appears to be correct.
There is a further technical point: The addition of anchors and of cables reaching from shore to shore provides added holding power to the ships only in theory, i.e. if the ships' tension on the anchor ropes and on the cables is exactly equal, but in practice, it is not possible to tune them to such a degree, especially not under the influence of changing winds, currents, eddies and undercurrents.
Because of the current and the lateral wind forces, they would have described a large curve allowing for a sort of horizontal sag of the cables in order to prevent the tension to increase indefinitely.
Only when he describes the bridges rebuilt after the storm he gives a single indication saying that the weight of the cables made of white flax was one talent per cubit what roughly translates into 26 kg/46 cm[29] or 56.5 kg per meter.
That alone is sufficient to discard the occasional opinion that the ropes had been produced and delivered in manageable lengths and had been spliced together on the spot.
If such ropes never had been produced, it is more than unlikely that the Persian general staff would have relied on a totally unknown method of production to be executed on swaying ships to build bridges of vital importance for the whole campaign, in particular since everybody involved was aware that any failure could result in his being beheaded.
[41] In certain densely forested parts of the US and of Canada, however, wooden roads have been covered by a layer of earth to protect the wood from deteriorating, which appears to have provided some comfort for the horses and carriages.
[47] The three openings for the passage of small ships probably have been made by inserting higher triremes into the line of penteconters or commercial vessels.
Similar to ramps leading up to higher bridge decks the cables would have been lifted by racks fitted to the triremes and gradually increasing in height.
It is left to speculation whether and to what extent ships, cables, ropes and logs were recovered, saved, repaired and reused.
During this time, the army waiting at the shore would have got into a very serious situation, since the provisions of food, fodder and water had not been calculated to cope with a prolonged stay.
This may lead to the assumption that the bridges told to have been destroyed by a storm were used by Herodotus only as a pretext for his vivid description in all details of an outburst of rage of the great king Xerxes and even to quote his furious speech in full.
