The Nazis cut the last direct railroad between central Russia and the Caucasus. Hereafter any oil flowing from the Caucasus to Russia must go by barge through the Caspian Sea and then up into Siberia.
Vagif Agayev et al.:
World War II and Azerbaijan by Vagif Agayev, Fuad Akhundov, Fikrat T. Aliyev and Mikhail Agarunov: On the eve of what came to be known as "The Great Patriotic War," Baku was the cradle of the Soviet oil industry, and as such, the major supplier of oil and oil products. In 1940, for example, 22.2 million tons of oil were extracted from Baku which comprised nearly 72% of all the oil extracted in the entire USSR…. During the first year of the war, Azerbaijan produced 25.4 million tons of oil-a record for the entire history of its oil industry…. By the end of the year, so many engineers and oil workers had left for the war front that positions had to be filled by women. By the summer of 1942, more than 25,000 women or 33% of all the workers were working 18 hour shifts in the oil industries. At refineries and chemical plants, the percentage of women was even higher estimated 38%. By 1944, women's participation had grown to 60%. Veterans and retirees also returned to the oil fields to help as much as they could…. Baku sailors were desperate to find new ways to get the oil to the war front. Since there weren't enough tankers to do the job, they improvised ways to tow cisterns across the Caspian Sea to Krasnovodsk, Turkmenistan….
Hitler was determined to capture the oil fields of the Caucasus including those in Maikop (Russia) and Grozny (Chechnya). But most of all, he wanted Baku. Hitler was obsessed with oil….
[B]y late July 1942, Hitler's quest for Baku seemed well on its way to achieving his goal. The Germans had already captured the city of Rostov and severed the oil pipeline from the Caucasus. On August 9, they reached Maikop, the most westerly of the Caucasian oil centers-which turned out to be quite a small source for the Germans. Even under normal conditions, Maikop's production was only one tenth that of Baku's. However, before withdrawing from the city, the Russians had thoroughly destroyed the oil fields and supplies and equipment….
Hitler's generals presented him with a large decorated cake which depictedthe Caspian Sea and Baku. Documentary films show how amused Hitler was at the gesture and how he chose the most desirable piece-Baku-for himself. Fortunately, for Azerbaijan and the Allies, Hitler's attempt to devour Baku was confined to the icing on this cake….
In the summer of 1942, the threat of attack became so strong that the Soviet authorities decided to terminate drilling operations to evacuate the most valuable machinery and equipment further East. By autumn, 764 wells in Baku were sealed and 81 complete sets of drilling equipment together with the personnel were transported to Turkmenistan….
Another problem inseparably tied to fuel production was its transportation. By the summer of 1942, the enemy had blocked the main railways through which oil and its derivative products were transported. Thus, alternate means of transport had to be found via the Caspian and Volga water way. When the Germans also succeeding in blocking this route, transportation was routed through Central Asia. But the front couldn't wait. Aircraft, armored carriers, trucks, and tanks all needed fuel. Then the naval experts of the Baku oil-tanker fleet performed an incredible feat. For the first time in the world's history, they began towing a floating railway of oil tankers (wagons) from Baku to Krasnovodsk (Turkmenistan) as well as several thousands tons of oil reservoirs from Makhachkala (Dagestan) to Krasnovodsk.
The fleets were extremely overloaded. For example, the amount of oil transport in July 1941 exceeded 10 million barrels of crude oil and fuel. This amount was beyond the technical capabilities of the tanker fleet in Baku. But the demands from Moscow did not take into account the physical limitations. It was then that Baku naval experts hit upon the idea of attaching whole tanks and cisterns to each other by steel ropes and lowering them into the sea by cranes and towing them by steam tugs. This had never been done before in any place in the world and it enabled them to tow up to 35 cisterns together or 3 huge oil tanks (5 ton capacity) with a single tugboat.