Xerxes' Pontoon Bridges

The pontoon bridges across the Hellespont were two floating bridges, the BC was built on the occasion of his campaign against Greece by the Persian king Xerxes I in 480, to the greatest army of the time from Asia across the Hellespont ( today's Dardanelles ) in which at that time also persian controlled Thrace ( in today's European part of Turkey, Eastern Thrace see ) to go.

During the Greek of the historian Herodotus in his histories reported bridge as such is generally accepted, there are many doubts about the details described in detail by him.

The bridges in Herodotus' Histories

Herodotus describes that the already planned campaign of Darius I was prepared for years. He mentioned that Xerxes ordered the provision of ships for the bridges and the manufacture of ropes made ​​of papyrus and of white flax.

While Xerxes marched with his army still at Sardis to Abydos, then a major port city on the Hellespont, two bridges were built from there to the opposite promontory at Sestos, one of the Phoenicians with ropes made ​​from flax and by the Egyptians with ropes made ​​of papyrus. Herodotus gives the length of the bridges with seven stadia, which would correspond to about 1300 m.

Both bridges were destroyed immediately after completion of a storm. Xerxes was so enraged that he ordered to punish the Hellespont with 300 lashes to throw shackles into the sea and to behead the two builders of the bridge.

Two bridges were under new supervisors then turn built from Pentekonteren and of triremes, the former warships, one of 360 ships and one further south on 314 ships, which were held by very large anchors in position .. have been for the passage of smaller ships three openings released. The large ropes were placed and fixed on the ships. This time, two flat cables and four papyrus ropes used for each bridge and tensioned by winches. The flat cables have weighed a talent per cubit and had been so much harder than the papyrus rush. Cross over the ropes and wooden planks were laid, and finally covered with brushwood with rammed earth, so that was a kind of road. On both sides of screens were installed, so that the horses were not afraid at the sight of the water.

The army with footmen and horsemen crossed the Hellespont in the northern bridge, the convoy with pack animals and support staff used the southern bridge. The crossing lasted seven days and seven nights

According to Herodotus History Xerxes are the bridge: after the failure of his campaign, he feared that the Ionians or Greeks could have destroyed the bridge. The Greeks in turn took counsel whether they should destroy the bridge. However, as a part of the Persian army was on the retreat to the Hellespont, they found only the remains of the destroyed by the storm bridges. Xerxes succeeded in spite of a storm by boat return to Asia.

Particulars

While Herodotus for good 30 years ago by Darius I built pontoon bridge over the Bosphorus hardly the place and any details indicating amazed at the wealth of details on the Hellespont bridges that give a vivid picture of the bridge with only a superficial reading. On closer inspection, almost every detail of bridges subject of questions, discussions and doubts, even if Herodotus' picture of the bridges is also reflected, and reproduced on the internet. One can therefore also its presentation less than sober, engineer technically correct description of bridges view than as decoration of the size of Xerxes I, which leaves the Greek victories seem all the more important to him.

Dardanelles

The flow at the surface towards the Mediterranean is specified with an average of 1 ½ knots, but is very dependent on the wind. Also by the wind caused the water level can rise up to 60 cm. At the bottom is an undercurrent flowing in the opposite direction. Especially with headlands occur frequently eddies and shoals.

The present narrowest point of the Dardanelles between Çanakkale and Kilitbahir (40 ° 8 ' 41 "N, 26 ° 23' 50 " O40.14469880305626.397314071667 ), 1.4 km wide and up to 91 m deep, but also has the strongest flow and in seafaring is considered the most difficult part of the strait. Çanakkale was only founded in the Ottoman period on the gravel delta one coming from the mountains, often torrential in winter flow ( which is now tamed by the Atikhisar dam ). Years ago, around 2500, the gravel delta was probably not as far advanced in the strait.

The mentioned by Herodotus Abydos lay on the Asian shore north of Çanakkale near the west extending into the strait Cape Nara ( Nara Burnu, formerly Nagara Burnu ) (40 ° 11 ' 47 " N, 26 ° 24' 8" O40.19628192333326.402227878611 ). The water depth is in the south and west of the Cape low, falls toward the center, but up to 103 m from. The flow runs in the middle of the strait with more than 2 knots to the southwest, but forming around the Cape Nara large cross-currents of.

Location of the two bridges

The stated by Herodotus place of bridges between Abydos and Sestos on the opposite bank is accepted by many historians. The British General Frederick Maurice, who visited the area in 1922, held from military considerations only one farther north beach for a suitable place for the construction of floating bridges, which would then, however, had a length of more than three kilometers there. Today's narrowest point before Çanakkale, however, should not come into question because of the then still wild mountain river could make everything rousing floods in no time.

Two bridges were needed, as the march of the huge army on the narrow streets of the Chersonese very far and pulling apart the convoy had to advance in parallel in order to not interrupt the supply of the troops with food, feed and water.

Ships

Herodotus writes clearly, whether Pentekonteren and triremes, so only warships, has been used as a floating body of the bridge. That seems to be universally accepted. However, it makes little sense to use warships for a task would have been more suitable for simpler and cheaper merchant ships because of its wider profile, deeper center of gravity and the higher freeboard. In a trireme the lower holes for the oars were only about 30 cm above the water line and were therefore provided with leather cuffs, which is rather unsuitable for the pontoon of a floating bridge.

The ships should also have all the same height to ensure a flat bridge deck. In addition, scaffolds were in the ship makes sense to compensate for differences in height and bear the burdens and derive in the center of the vessel, so that unsuitable for selective high loads vessel walls are not damaged. Even if the use of merchant ships is not discussed and therefore disregarded the bridges could have consisted almost exclusively of Pentekonteren and have been used because of their greater height only on both sides of the passages triremes.

Anchor

In floating bridges on rivers the ships are usually held by anchor at the bow and stern in their position, so seems Herodotus description of the anchor initially also credible. However, the depth of the Straits of Herodotus is not mentioned, although mentioned by later historians, but apparently nowhere discussed as a problem.

Anchor lines must have the more times the length of the water depth in order to avoid that the anchor tear or damage the ship. The ships in the middle of the Hellespont would then bow and stern must each have several hundred meter long anchor lines, so that a total of 674 ships allegedly would have been necessary for not only 1348 serious anchor, but also some two hundred miles anchor lines. It is quite questionable whether the time such amounts in the relatively short time could be produced at all. On top of that can be with so long anchor lines not prevent the ships schwoien and collide, especially when eddies play, and that the anchor lines of closely adjacent vessels entangled. Finally, it may not be possible, the anchor, it had still been stone baskets or even iron stock anchor, with their over-long lines to place so that the ships lie exactly in a row.

If one nevertheless from that described by Herodotus anchoring of ships, must be taken into account that every bridge had with their anchor lines requires an up to 900 m wide side stripes. But then would be on the shore at Abydos barely enough space for two bridges have been.

In addition, the security of the ships would bring both anchor lines and through to the shore reaching from shore ropes only theoretically an advantage when anchors and ropes are coordinated so that both have exactly the same tensile force, which can not be achieved in practice, but, in particular. under the influence of prevailing winds, currents and counter-currents But then overloaded the entire train on only one of the two elements, the other does nothing to backup.

It must therefore be assumed that the ships were held only by the long ropes into position and anchor were only used temporarily in the flatter areas to keep the ships until the ropes were installed and mounted on the ships.

Length of the bridges

The stated by Herodotus length of seven stadia, or about 1300 m is too short in any case.

At Abydos is the direct distance between the shores of approximately 2000 m. However, even this distance of 2000 m may not correspond to the length of the bridges. If this could not be held by anchors because of the great depth, only the attachment to from shore to shore -reaching ropes remained ( apart from the question whether a rope alone or several interconnected ropes had this length ). Because of the flow and the lateral wind loads but these ropes must have some slack so as not to grow to infinity the tension of the ropes on the fortifications on the banks. The ropes are therefore likely to have been about 5 to 10% longer than the distance between the banks - plus the length required for anchoring on the banks and, where appropriate, on the ships. This results required cable lengths of over 2200 m.

Assuming the width of a Pentekontere with 4 m, still remained with the 2200m long bridge from 314 ships about 3 m between the ships when you leave the specifics of the built triremes with passages in mind. This seems to be a reasonable value. At the bridge with 360 ships this configuration would result in a bridge length of almost 2520 m, which appears for the northern, not directly located on the Cape Nagara Bridge also a useful value to be.

Width of the bridges and the roads

Herodotus gives no indication of the width of the bridges and the roads leading through it. It is believed that Greek roads were then between 2.7 m and 3.6 m wide, so that the bridges have a width of 3.6 m can be considered. This allowed the march of four men or two riders side by side. A larger width would have no positive effect, as the road could not accommodate the incoming masses at the end of the bridge. It also advises against wide floating bridges, as they fluctuated even more and the already nervous horses made ​​even more afraid.

Ropes

Herodotus mentions the judgment given during the preparatory phase command for making ropes for bridge rather casually as an order larger quantities of commercial goods. Only in the description of the damage after the storm again built bridges he makes a single concrete indication that the over the papyrus ropes heavier flat ropes had weighed one talent per cubit, which can be translated roughly 26 kg/46 cm. That would be 56.5 kg per running meter. With different conversion methods to those which result from rope diameter 23 to 28 cm! Ropes with such a weight can no longer handle to ropes with a diameter such can hardly be bent and therefore not on - then probably not yet known - Roll cable reels or otherwise allow for transport. So you could also be only several meters thick bollards fix without breaking them. Herodotus seems to speak of through, from shore to shore -reaching ropes. A single cable of 2200 m would have a weight of 124.3 tons and would be so even today virtually impossible to transport.

Because such ropes are not manageable and therefore have no practical application, is not to assume that any rope makers of antiquity they had ever made ​​. For this reason alone is also occasionally expressed opinion untenable, the ropes have been manufactured and supplied in manageable lengths and been spliced ​​together only on site.

The idea, the ropes were made ​​only locally on the ships, is therefore likely to fail due to practical considerations. If such ropes were never produced, it is more than likely that you have embarked on a completely unknown mode of production to fluctuating ships to set up bridges, which were for the entire campaign is crucial, more so if the parties were aware that they might be beheaded in the case of failure. In addition, the manufacture of ropes requires a certain tension of the strands and the finished rope. Therefore it must be assumed that the ships would initially located close together so that the voltage can be achieved. In three or four ships that might be conceivable in a larger number in the open water lying, necessarily fluctuating ships should, however, the rapidly lead to significant damage to the ships and to serious disturbances of rope production.

Such a cable, as described by Herodotus to hook with the help of winches is excluded.

It must therefore be assumed that a wide arc forming ships with several, then ordinary ropes were connected. It is ultimately irrelevant whether a cable length only from one ship to the next or over several ships handed away. It is also irrelevant whether it was sufficient for the positioning of ships, to secure it to the bow and stern only with a rope. Otherwise you would similar to today's parallel wire ropes in suspension bridges several ropes tightly put together, if you made ​​sure that they are evenly loaded. To avoid confusion, you might have this cable bundle also wrapped, which may then have given the impression of an overly thick and heavy rope.

The function described by Herodotus of the ropes encountered considerable doubts. According to Herodotus, the ropes would have been used not only for positioning the ships, but also as a carrier of the lying crosswise on the ropes wooden planks. But every sailor tries to prevent ropes shame profiles, scrub or rub against something in order to avoid their premature wear. The constant movement of ships in waves and under the by marching army and retinue, the large load of soldiers and earth on the planks and their pressure on the tight ropes would have certainly led to her early break. Neither would have been possible with this construction is not a flat road. The ropes were hung by taking the high vertical loads between ships ( and without special supports within the vessels), so that the road would have formed a constant up and down. On top of that the Earth would be quickly collected in the troughs and would thereby increase the local loads on the ropes significantly. There was also no need for this construction: at a distance of not more than three meters between ships, the planks would also directly on the ships can be attached (parallel to the ropes ). This would be a more solid foundation for the road and would have prevented the premature wear of the ropes.

Bridge deck

Bohlen

The supporting bridge deck was formed by wooden planks, whose strength must be measured at least 10 cm. Since sawmills did not exist, it must have acted to split and raw -hewn logs in the wood planks. Then would be about 800 cubic meters, for the other around 910 cubic meters for a bridge, thus a total of 1710 cubic meters have been required. This corresponds to an average density of 0.5 t / m³, a weight of 855 tons.

Brushwood

The purpose of the cover of the wooden planks with brushwood is not recognizable. Perhaps the sticks should fix the earth.

Covering of earth

Was An all- wooden planks bridge in modern times, even without other covering than sufficient. In modern times, however, occasionally wooden streets were covered with soil to protect the boards against wear what was comfortable for riding and carriage. Thus, the hard-packed earth did not dissolve immediately under the horses' hooves, he must have had a thickness of at least 20 cm.

Load assumptions

With a 3.6 m wide bridge and ships with 4 m width and a gap to the next ship of 3 m accounts for each ship 3.6 x 7 = 25.2 m² bridge surface, the weight per square meter with 50 kg of wood and 360 kg earth is to accept and then is about 410 kg. Each ship would thus 25.2 x 410 = 10,332 kg plus the weight of 4 x 7 = 28 people, each weighing 90 kg to wear ( with luggage ) = 2520 kg, a total of about 13 tons, which was probably an acceptable load for that time ships.

Screens

To adjust the horses the view of the water, the bridges screens were mounted on both sides. Assuming that such a modesty panel is only 2 m high, results only for one side of the 2,200 m long bridge an area of ​​4,400 m². Even with minimal wind speeds resulting wind loads would not have been mastered with the former agents. In floating bridges modern times, simple railing slats or ropes have proven to be perfectly adequate to keep the horses on the bridge.

Passage openings

The three openings for passage of smaller vessels were probably produced in that higher triremes were inserted into the series of Penteconteren or commercial vessels, and the continuous ropes were raised, similar to a bridge ramp of goats on the triremes slowly to the level required for the passage. Since the ships could tilt her masts easily, should a drive-through height of 2 m above the water line have been sufficient. In wind -related increase in the load on the ropes the triremes would indeed pressed something into the water, but that only lasts as long as the wind blows.

Storm damage

From Herodotus, the storm had completely destroyed the bridges, little concrete can be deduced despite the seemingly clear wording. It is not clear whether and to what extent ships, ropes, planks, etc. could be salvaged, repaired and reused. It can be made its report, but also not be inferred that all the parts had to be procured. The preparations for the bridge have taken years, so replacement deliveries of ships, ropes, anchors and wooden planks would have at least taken months to complete. But the laying of the planks and the soil must have lasted a couple of days originally. Even if one assumes that everything could be repaired and no deliveries were required to be expected with a repair period of several days. During this time, would have been for the waiting on the shore army but give a very serious situation because the food stocks, food and water were not calculated for a longer stay.

In Herodotus' report reveals that the first bridges are barely mentioned and reported again as destroyed, while the later -built bridges are described in detail, but without losing a word about the duration of the repair. This can lead to the assumption that the allegedly destroyed by the storm bridges Herodotus only served as a springboard to then immediately describe one outburst of the great king Xerxes with numerous details can thereby even play the King's Speech in the text.