Good answer by Smirnov, but to answer the unasked question "why was it difficult to find that information?" answers a lot more questions. Baku in on the Caspian Sea, below sea level, and the oil flows up out of the ground. It produced half the world's oil prior to WWII and continues to be important. Besides the oil fields in Arab countries, control of the region also meant containing Baku pipelines. What's the deal with the war in Syria? Pipelines from Baku. Turkey has been very important to limiting the amount of "Soviet" oil available as well by controlling access to the Mediterranean. Ukraine is the northern route to Europe and may, just may, have something to do with instability there and keen US involvement.

So the energy wars have been going on for a long time and are the source of current US military action. Not just to control sources but to control routes for delivery (pipelines). Except it is sold to the American people as "human rights abuses" and to stop madmen gassing their own people (with gas we and the Russians gave them just for that), rather than the pipeline wars it really is. Just look at the timing of plans to sell US controlled/produced LNG and oil to Europe compared with "tensions" in Ukraine. So real people die, trillions spent on weapons and the fuel to run the military. 500% fuel cost increases to DOD during Bush (https://fas.org/sgp/crs/natsec/R40459.pdf).
History during the Oil Age is highly conflated by commercial interests while citizens are given (and children taught) "noble" reasons. Soviet Revolution, who cares if the peasants took power from a ruling monarchy (the story we tell of ourselves) but without the Baku oil fields there would have been less reason to brand Communism a crime against nation, God, decency (still have the problem of organized labor that the manufacturing industry couldn't abide). But North and South, East and West United States industry and finance (don't minimize Wall St's role in wanting to control market of energy) could unite to tell a story about the Evil Reds. While Saudi Arabia and Iraq much mentioned in common person's understanding of oil supply, Baku (remember, half the supply) was not talked about, treated as if it didn't exist. US funding of early attempts at Azerbaijan independence is unknown but we can track US involvement with Turkmenistan (other side of the lake) and it's Most Favored Trade Status with us since military investment in the dictatorship began in 2001. They have pipelines too, that can go West or to China (beyond US control). Ongoing Myanmar tragedy is concurrent with Chinese pipelines to the Indian Ocean that pass through and require major building in the homeland of the Rohingya people in Rakhine state. Yeah, current news is that millions have been evicted. Blah blah blah.
Point is we hear the "human tragedy" part and not the pipeline part. Baku, Azerbaijan has been a major player with almost all information about it expunged in the USA, covered over with other propaganda, while pipeline access is controlled.
And Germany was really into wood gas to run its trains, securing timber land rather than natural gas supply. Only other resource in Ukraine mentioned is farmland.

Good answer by Smirnov, but to answer the unasked question "why was it difficult to find that information?" answers a lot more questions. Baku in on the Caspian Sea, below sea level, and the oil flows up out of the ground. It produced half the world's oil prior to WWII and continues to be important. Besides the oil fields in Arab countries, control of the region also meant containing Baku pipelines. What's the deal with the war in Syria? Pipelines from Baku. Turkey has been very important to limiting the amount of "Soviet" oil available as well by controlling access to the Mediterranean. Ukraine is the northern route to Europe and may, just may, have something to do with instability there and keen US involvement.

So the energy wars have been going on for a long time and are the source of current US military action. Not just to control sources but to control routes for delivery (pipelines). Except it is sold to the American people as "human rights abuses" and to stop madmen gassing their own people (with gas we and the Russians gave them just for that), rather than the pipeline wars it really is. Just look at the timing of plans to sell US controlled/produced LNG and oil to Europe compared with "tensions" in Ukraine. So real people die, trillions spent on weapons and the fuel to run the military. 500% fuel cost increases to DOD during Bush.
History during the Oil Age is highly conflated by commercial interests while citizens are given (and children taught) "noble" reasons. Soviet Revolution, who cares if the peasants took power from a ruling monarchy (the story we tell of ourselves) but without the Baku oil fields there would have been less reason to brand Communism a crime against nation, God, decency (still have the problem of organized labor that the manufacturing industry couldn't abide). But North and South, East and West United States industry and finance (don't minimize Wall St's role in wanting to control market of energy) could unite to tell a story about the Evil Reds. While Saudi Arabia and Iraq much mentioned in common person's understanding of oil supply, Baku (remember, half the supply) was not talked about, treated as if it didn't exist. US funding of early attempts at Azerbaijan independence is unknown but we can track US involvement with Turkmenistan (other side of the lake) and it's Most Favored Trade Status with us since military investment in the dictatorship began in 2001. They have pipelines too, that can go West or to China (beyond US control). Ongoing Myanmar tragedy is concurrent with Chinese pipelines to the Indian Ocean that pass through and require major building in the homeland of the Rohingya people in Rakhine state. Yeah, current news is that millions have been evicted.

Blah blah blah.

Point is we hear the "human tragedy" part and not the pipeline part. Baku, Azerbaijan has been a major player with almost all information about it expunged in the USA, covered over with other propaganda, while pipeline access is controlled.

And Germany was really into wood gas to run its trains, securing timber land rather than natural gas supply. Only other resource in Ukraine mentioned is farmland.