The very dynamic theory of politics not between people or peoples of a region, but of the regions themselves. They can be as relatively simple as the 50 States of the USA and the Federal Government of that same entity to the highly complicated, such as the oil-producing Gulf States or the former USSR's constituent countries. Geo-Political relationships can also range from the fully justified to what would appear to be morally repugnant, but the actions themselves are purely neutral; the results of the actions are what should be subject to judgement calls.
The USA allying with the USSR in WW II ( Germany was at the time a far bigger menace. Needless to say, the USSR's ideology would be eternally at conflict with ours.)
The Cold War that followed WW II was classic Geo-Politics at its best. Due to MAD (Mutual Assured Destruction) ideology, there was no safe way the US and USSR could directly confront each other. So came the period of Tinpot Dictators supported by both sides and at least two major proxy wars ( Korea & Vietnam). The support to these oft times vicious and repressive regimes was concerned with controlling as much of the world as possible versus tending to the individuals needs in those countries.
With the fall of the Shah and the ascendancy of Ayatollah Ruhollah Khomeini, Iran posed a serious threat to Gulf stability. Though at no time would Saddam have been considered a friend, his military could serve to defuse the potential Iranian flashpoint. As such he was aided in his war with Iran (1981-1988). The two countries laid waste to each other, leaving the rest of the gulf in relative peace.
One of the most important geo-political happening in the present day is once again the Gulf states. By no means should the Shiekhs' of theose countries be called our friends; Islamic Shari'a law is in conflict with much of what the US Republic holds dear, and there are factions within those countries that would like to see the USA destoyed. But as long as they are in power though, they represent a stable supplier of a needed world economic commodity (Oil). As long as this is a needed commodity, do not expect too much change from that region. Iran also is once more a potential flashpoint in the region, nuclear ambitions aside.
Israel is not necessarily our friend either, though at least society-wise Christianity sprang from Judaism and politics-wise a Parliament ( Knesset) is closer to our Congress then Shari'a law. Even though that is the case, Israel still has its own agenda ( A safe haven for those of Hebraic descent), and at times they do not always work in the best interest of the USA. They have been overly heavy-handed at times, even if they also have made attempts to settle the mater using detente.
A full discourse on this topic would take up one book if not several; this is perhaps a basic definition of the term to perhaps invoke more independent research from the reader.