Why did Egypt treat Nubia differently from Syria/Palestine and her northern neighbours in the Middle Kingdom?

Little actual detail of MK international trade is known, although from many Egyptian items found in the Levant and items with foreign influence found in Egypt, we can understand its scale and importance. Relations with the North-East are not well recorded, although records of an expedition to Punt exist. Egypt was remote from the great international trade routes and had to establish contact with it's neighbours in the North-East to gain access to the resource (such as cedar, as well as the more decorative items such as silver and lapis lazuli). The primary trade route was the "Way of Horus" to Palestine, which connected to the major trade routes from the far-east (see temple at el-Tod) and also to Mediterranean traders.

During the OK Egypt's involvement in Nubia was predominantly peaceful and focused on trading commodities from the distant parts of Africa and for local minerals. Buhen, close to the second Cataract, was a trading centre and Nubia's name probably originates from the word Nub meaning Gold. After the OK ended the C-Group people in Nubia gained independence and, over time, became stronger - ending Egypt's control and access to minerals and restricting the trade in ebony, animals, ivory, workers etc.

Amenemhat I begun the 12th Dynasty with a policy that continued through the period - it was a requirement of kingship. He established the "Wall of the Ruler" and its also thought that the same approach was used on the western border (Qaret el-Dahr). He instigated military expeditions into Nubia (at the end of his reign) and we know from the Tales of Sinuhe that Senusret was campaigning in Libya at the same time. From the militaristic policy we surmise that the goal was to re-establish control and frontiers - probably because of incursions during previous periods. Senusret I continued his father's policy in Nubia, under the leadership of General Mentuhotep, extended control to Buhen; this was extended by Senusret III to Semna which allowed total control of the Nile and curtailed the Kushite King's ambitions. Although he captured the city of Skumm in the Levant (location isn’t known) there doesn’t seem to have been a strong desire or need to extend physical control into the Levant - whereas in Nubia a series of fortresses and garrisons were necessary to hold and control trade and mining in the area. Senusret's military policy bequeathed a country extending from Sinai to the 2nd Cataract (see the aerial view of the 60 mile long second cataract and the fortresses of Semna) which benefited from internal and external peace.

Items from the major eastern trade routes did not originate locally and were bartered for. However the Gold, amethysts and hard-stone in Nubia was local which could explain why Egypt felt the need to physically control that region - especially with the threat of the Kushite King's influence. It is important for any state to ensure that borders are well defended and as remote from it's heart-land as is possible.

Through this period of time contact with Asia was generally focused on trade and contact with the South was controlled by force-of-arms. I think that this was the policy because Egypt used the 'appropriate' technique, for each region, that would protect it's frontiers and support its economy.