Historically, the answer would have been because of the way the Zagros Mountains cut across the Iranian heartland. Today, Iran has a complex train and highway network that links the north and south, making travel much less difficult.
It was hard because it was a swampy land and the climate was harsh.
was it a change of weather, while traveling/migraiting
It would probably be difficult traveling in a Space Shuttle, because of the gravity. There is basically no gravity unless you are on earth... That and the face that you would be so confined in such a small space, and that is something that I would never be able to do, because I am very bad at being in small spaces especially for long periods of times!
Because they were traveling in the middle of winter and some of the troops did'nt have any shoes or comfortable clothing.
The location of the canal made it difficult to build because of its distance from the countries buliding it.
Because it can be painful, tiring or boring. Or just difficult.
Because all lanthanide's have almost similar physical as well as chemical properties.
This is a physical change: the bread is not being chemically altered, and would have the same nutritional value whether eaten from the loaf or the slices. It would, however, be difficult to exactly reverse this physical change because of the nature of the product.
They are trying to. ASMR is difficult to research because the effects of it are psychological rather than physical.
Many others physical conditions like that are difficult to recognize. The science moves slowly forwards because there are still much to discover.
The Ancient Greeks traveled by the sea because the land was to mountainous to travel by foot. The Ancient Greeks traveled by foot, cart, chariot and ship.
No, malleability is a physical change because the object can be changed back into it's original shape (although this may be difficult).