I've found many sources explaining the details of the USA's military presence abroad; yet, nothing about how or when they got there.
Even the number and locations of all the bases vary wildly (understandably so). I've heard estimates range from 600 to 1000+.
https://en.wikipedia.org/wiki/List_of_United_States_military_bases https://www.globalresearch.ca/the-worldwide-network-of-us-military-bases-2/5564
However, what I'm most interested in learning is how and when they were established. They only lead I've been able to find is the "Destroyers-for-bases deal" from 1940, in which the UK agreed to give land rights in colonial territories to the US, in exchange for destroyers which it could use against Nazi Germany.
https://en.wikipedia.org/wiki/Destroyers-for-bases_deal
Any response will be greatly appreciated!
P.S. I'm aware Wikipedia is not considered a legitimate source, my aim was only to provide an easy jumping-off-point for readers who are not well versed in the topic.
It might be useful to go on a case by case basis, but there are some general rules of thumb when it comes to US military bases abroad.
Economically/diplomatically/militarstically, an abroad US military base can provide mutual benefit to the US and whatever country hosting said base.
One advantage is just inherently having stronger diplomatic relationships with each other because of the connection.
Depending on the deal, a US military base could be paying for the land it is situated on.
There is also the potential for military members to spend their paychecks on the local economy.
Hosting a US military base makes it a lot easier to buy military equipment(which also profits the US) and get military advising.
Just the fact that it exists is also a good deterrent from invasion or other hostile action. If there is a mutual enemy or competitor, the country in question gets protection by hosting the US military, while the US also gets to pre-empetively prevent any competition or potential threats from gaining an advantage from a theoretical invasion.
Usually, both the US and any countries in question would consider to what extent these advantages apply or are needed, and then make a diplomatic deal that results in the creation of an abroad US military base.