Autarky

Autarky is economic self-sufficiency. A national economy which can independently exist is an autarkic economy. Truly autarkic economies don't rely on international trade.

No national economy in the contemporary world is fully autarkic. North Korea probably comes closest, with its state ideology Juche (roughly translated as "self-reliance") containing a heavy dose of it. However, while the final goal is full autarky, North Korea still does not have a true autarkic economy, since it trades with China and relies heavily on grain imports and international aid to prevent its population from starving to death.

Autarky has some military benefits. Most of the world's major powers during World War II (1939-1945) relied on it, with it being most pronounced in the Axis powers (German and Japanese imperialism were motivated in large part by resource concerns) but with the US and Britain also implementing autarkic wartime measures. When submarine corsairs throttle foreign commerce or blockade ports, autarky starts to look attractive - provided one can grow enough food and mine enough essential resources. The communist world, particularly under the Stalinist model of "socialism in one country", also leaned heavily on autarky, with the Eastern Bloc existing effectively separate from the rest of the world outside the international black market. Then too, what happens if other countries don't want to trade? Newly-independent Haiti had the temerity to abolish slavery and institute a government run by people with dark skin in the early-19th century - so international investment there, and trade, suffered severely. Apartheid South Africa, during its late-period global-pariah status, was effectively pushed into autarky as boycotts, divestment, and sanctions effectively isolated it from global trade. Spain was for some years after World War II also almost entirely isolated from the rest of the world due to Francisco Franco's fascist dictatorship. As autarky is a (somewhat) sensible policy if the whole world actually is out to get you and tries to subjugate you through embargoes, it often gets favored by deranged leaders suffering from some form of paranoia. Albanian dictator Enver Hoxha (in office from 1944 to 1985), who came to believe that NATO, the Soviet Union, and ultimately even China were out to get him, thought that only autarky and building millions of bunkers could help his country survive the inevitable invasion(s).

In short, the most common way autarky presents is as a nationwide equivalent of prepping.

Energy independence
While energy independence — something you hear cited as justification for both expanding renewable energy and drilling for oil in the Alaskan wildlife reserves — is indeed an important, if not the most important, component of autarky, it is not the same and the aims are different. While autarky takes "dependence" on foreign trade as bad per se and tries to replace imported resources and goods with domestically produced things even if they are clearly inferior, energy independence allows a country to be strategically and economically independent of a handful of large suppliers. In theory, a similar effect to energy independence could also be reached by diversifying the countries from which energy resources are bought. However, this is usually impossible as long as energy relies on oil to a measurable degree, as oil is largely in the hand of a few countries.

One particular recurring trend in modern autarky attempts is, as many countries have abundant coal reserves but only a few countries have significant oil resources.