A thread on Russia's rail supply lines to its occupying forces in Ukraine - how these have been affected by the recent Kharkiv offensive, and what's likely to happen next if, as I expect, Ukraine moves next to retake northern Luhansk oblast. 🧵

The hubs of the rail network supplying Russia's occupation of northeast Ukraine are laid out like a pyramid. At the top is the primary supply hub Voronezh, then the junctions of Stary Oskol and Liski, and finally the forward supply hubs of Belgorod, Valuyki and Millerovo. /2

Belgorod till recently was the most important forward hub and most in the news. Its rail routes west to Sumy, south to Kharkiv and southeast to Kupyansk made it a natural invasion staging ground. But after the Kharkiv offensive, all those routes lead to liberated territory. /3

And now the route from Belgorod to Russian occupation forces is much longer. The options are to loop by train back through Stary Oskol, or to go by road first to Valuyki. In short, aside from inertia, Russia has no more reason to use Belgorod as a forward hub. /4

Meanwhile Valuyki has gained weight. The line from it southeast across Luhansk oblast is now the main supply line for Russians in the northeast. By winding through Luhansk, this line can also supply Lysychansk (east of Sloviansk), recently cut off from routes via Kupyansk. /5

For that reason, the rail line southeast from Valuyki is likely to be among the first targets of the next offensive. Troitske, the northmost major town on the line, is about a 90-minute drive from Kupyansk. (From there it runs to Starobilsk.) /6

Russia's one other northeast forward hub, Millerovo, is reached by a different line from Voronezh via Liski. This line runs across a small part of Ukrainian territory, so Russia is likely to try to cling to that area even if it loses the rest of northern Luhansk oblast. /7

Millerovo has another problem: its line to Luhansk enters Ukraine north of the Donets, an area Russia might lose if it loses northern Luhansk oblast. Ukraine tenaciously held the rail junction at Stanytsa Luhanska (under the "n" of Luhansk) from 2014 until this year. /8

In the southeast the hub at Gukovo is reached from Millerovo, Rostov - the area's main supply center - or Volgograd to the east. If Ukraine cuts the line from Voronezh to Millerovo, the quickest way by train from central Russia to SE Ukraine would be via Volgograd to Gukovo. /9

Turning finally to the south, the crucial rail hub is Dzhankoy - in the news last month as one of the targets of a series of still unexplained long-range strikes by Ukraine in Crimea. Both rail lines into mainland Ukraine from Crimea come from Dzhankoy. /10 end