Russian natural gas exports via the Soviet-era pipelines running through Ukraine to Europe were halted in the early hours of New Year’s Day. The transit deal expired, and Moscow and Kyiv have been unable to reach a new agreement to continue the flows.

The shutdown of Russia’s oldest gas route to Europe marks the end of a decade-long strained relationship, which began with Russia’s seizure of Crimea in 2014. Ukraine ceased buying Russian gas the following year.