What is the citadel? The military operation “Citadel”.

What is the citadel? How does it differ from the fortress or castle? When and who carried out the military operation “Citadel”? All these questions can find answers in our article.
Brief history of fortifications
People began to defend their homes, villages of ancient times. Most first fortification structure can be considered a settlement – a system of earthen walls, which was erected around the settlements. Later they were surrounded by wooden palisades, later – stone walls and towers with loopholes.
What is the citadel? The military operation “Citadel”.
In the Middle Ages begin to build huge castles, with high and strong walls, battlements, bastions, redoubts and ditches filled with water. What is the citadel? When did it arise? Let’s try to understand this issue.

The fortress-citadel: What is it?
The earliest citadel there in the cities of the ancient Indus Valley Civilization. These powerful reinforcement not only protect people, but also embodied the strength and power of the state.
To answer the question, what is the citadel, refer to the etymology of the term. Translated from Italian “citadel” (cittadella) – is a small fortified town or village. However, there is another version of the origin of the word. Some researchers associate the term with the Latin word civis “, which translates as” citizen. ”
In terms of architecture, citadel fortress called good that protects the city, or inside, the most reliable part of the castle, where residents can take refuge in the most extreme cases. Citadel usually can make defense against enemy troops alone.

What is the citadel? The military operation “Citadel”.
A landmark feature of the citadel is that it appears the latest stronghold of the defense of the city, when all other facilities and defenses are taken. Citadel must have sufficient space to accommodate not only military garrison, but needed rations (food, weapons and ammunition).
Synonymous with the word “stronghold” is an architectural term “fire.” This name can often be found in Russian chronicles XIV-XVI centuries. The term most likely comes from the word “castrum” – “castle”.
How different from the citadel fortress?
Among scientists and researchers do not have a single and coherent system of concepts concerning certain elements of fortification.
The fortress (or castle) – a general name for the whole system of fortifications established around the city, village or feudal palace. At the same time, the citadel is only part of a separate element of the defense system.
Thus, if a first protective outpost understand the position of any strength, the citadel – a last point of defense. If the city walls and outer fortifications were captured by the enemy, the garrison could continue defending it in the citadel.
What is the plan of “Citadel”?
July 5, 1943 began a massive strategic offensive forces of the Wehrmacht on the position of Soviet troops in the Kursk bridgehead. This military operation was in the name of history – a plan of “Citadel”.
What is the citadel? The military operation “Citadel”.
The task of the German headquarters was the most rapid encirclement of the enemy and their immediate destruction. However, the Red Army command has been able to organize a competent and successful defense. And, at the end of six days after the operation, the situation for the Germans was extremely disappointing. The result of the offensive “Citadel” became a complete failure for the Nazi troops.
Finally
Now you know what a citadel, and how it differs from other fortification elements. This is the most reliable and fortified part of the fortress, which serves as the last refuge for the garrison defending the city.

Interesting facts about physics. Physics around us: interesting facts

What science is rich with interesting facts? Physics! Grade 7 – a time when students begin to study it. For serious subject seemed so boring, we propose to start learning interesting facts.
Interesting facts about physics. Physics around us: interesting facts
Why seven colors in the rainbow
Interesting facts about physics may apply even rainbows! Number of colors it has identified Isaac Newton. Phenomena such as rainbows, interest in Aristotle and Persian scholar essence it opened in 13-14 century. Nevertheless, we are guided by the description of the rainbow, which made Newton’s work “Optics” in 1704. He identified the color of a glass prism.

If you look closely at the rainbow, you can see how the colors flow smoothly from one to another, creating a huge number of shades. And Newton initially identified five key: purple, blue, green, yellow, red. But the scientist had a passion for numerology, and therefore wanted to bring the number of colors to the mystical number “seven”. He added to the description of two rainbow colors – orange and blue. So out semybarvna rainbow.
Form liquid
Physics around us. Interesting facts may surprise us, even when it comes to such familiar things as ordinary water. We all used to think that liquid does not have its own form, this says even a school textbook on physics! However, it is not. The natural liquid form – the ball.
Interesting facts about physics. Physics around us: interesting facts
The height of the Eiffel Tower
What is the exact height of the Eiffel Tower? This depends on the weather! The fact that the height of the tower varies by as much as 12 centimeters. This is what a hot sunny weather, the structure is heated, and the temperature beams can reach 40 degrees Celsius. And as you know, the substance may expand under heat.

Desperate scientists
Interesting facts about physicists can not only be fun, but also talk about their dedication and devotion to the beloved. In the study of electric arc physicist Vasily Petrov removed the top layer of skin on the fingertips to feel weak currents.
But Isaac Newton introduced in your own eyes to understand the nature of the probe. The scientist believed we see that the world presses on the retina.
Interesting facts about physics. Physics around us: interesting facts
quicksand
Interesting facts about physics can help to understand the properties of such interesting things like quicksand. They are nenyutonovskuyu liquid. A person or animal can not dive into the quicksand entirely due to the high viscosity, but get out of it is very difficult. To pull up with sand zybucheho need to make an effort comparable to a car show.
It can not sink, but the danger to life are dehydration, sun, tides. When injected into the quicksand need to lie back and wait for help.
Interesting facts about physics. Physics around us: interesting facts
Supersonic speed
You know who was the first device, preodolevshee sound barrier? Straight shepherd whip. Click scaring cows is nothing like cotton in overcoming the speed of sound! If a strong stroke the tip of the whip moves so fast, creating a shock wave in the air. The same thing happens with the plane moving at supersonic speed.

Photonic areas
Interesting facts about the physics of black holes and the nature of those who sometimes can not even imagine implementing theoretically calculations. It is known that light consists of photons. Getting under the influence of gravity to form a black hole photons arc, an area where they begin to revolve in its orbit. Scientists believe that if you put a person in such a photon sphere, he can see his own back.

Scotch
It is unlikely that you rozmotuvaly tape in a vacuum, but scientists in their labs did. I found that there is unwinding at visible light and X-rays. The power of X-rays is that even allows you to take pictures of the body! But why is this happening – a mystery. A similar effect can be seen in the destruction of the asymmetric bonds in the crystal. But here’s the thing – no crystal structure in the adhesive tape no. So scientists have come up with another explanation. Do not be afraid to unwind the tape at home – no radiation in the air occurs.
Experiments on humans
In 1746 the French physicist and, concurrently, the priest Jean-Antoine Noll studied the nature of electric current. The scientist decided to find out what the rate of electric current. But how to do it in terms of the monastery
Physicist invited to experiment 200 monks, combined them with iron wire and rozryadyv poor fellows in the battery of a newly invented Leyden jars (they are the first capacitors). All the monks responded to both strike and it made clear that the current rate is extremely high.
Interesting facts about physics. Physics around us: interesting facts
Brilliant Losers
Interesting facts from the life of physicists can give false hopes unsuccessful students. Among negligent students walking legend that Einstein was the most famous real Losers ill knew mathematics and general flunked exams. And nothing, became world famous scientist. We hasten to disappoint: Albert Einstein began to show exceptional mathematical ability as a child and had knowledge that far surpass the curriculum.

Perhaps the rumors of poor academic achievement emerged that he immediately joined the Higher Polytechnic School of Zurich. Albert brilliantly passed examinations in physics and mathematics, but in other disciplines required number of points not scored. Pulling knowledge from the relevant items, future scientist successfully passed the exams next year. He was 17 years old.
Birds on a wire
Have you noticed that birds like to sit on the wires? But why they do not die from electric shock? The fact that the body – not a good conductor. Bird paws create parallel connection, through which runs a small current. Electricity prefer wire that is the best guide. But when the bird is a touch element, such as a grounded support, as electricity is sent through her body, leading to death.
Interesting facts about physics. Physics around us: interesting facts
Hatches against fireballs
Interesting facts about physics can remember even when viewing the urban racing “Formula 1”. Sport race cars moving at such high speeds, between the bottom of the car and the road surface creates low pressure, which is enough to lift the manhole cover into the air. That’s what happened to one of the local races. Manhole cover faced with the following machine fire, the race was stopped. Since then, in order to avoid accidents manhole covers are welded to the rim.
Natural nuclear reactor
One of the most important branches of science – nuclear physics. Interesting facts are here. Did you know that 2 billion years ago in the area acted Oklo natural nuclear reactor true? The reaction proceeded 100,000 years before the uranium lived not decreased.
An interesting fact is that the reactor was self-correcting – to mine uranium ore fell into the water, which played the role of moderator neurons. With active during the chain reaction of water boiling dry reaction weakened.