(NEXSTAR) – Despite being the second-largest city in Ukraine, the northeast city Kharkiv is particularly threatened as Russia stages an invasion of the country at the order of Vladimir Putin. Attacks began in the early morning hours Thursday, when bombs sounded in a dozen Ukraine cities.

Kharkiv, which has a population of around 1.4 million people, is only about 26 miles from the Russian border. The city – once a capital – is considered a cultural hub, known for its wealth of art, music and history.

The city is also a prime target for Russian takeover.

“Kharkiv has long loomed large in President Vladimir V. Putin’s view that Ukraine is no more than an appendage of Russia unjustly snatched away…” writes the New York Times‘ Andrew Higgins.

Here are the key reasons Kharkiv is so vulnerable.

Proximity

Most obviously is Kharkiv’s closeness to the Russian border: The nearest Russian city, Belgorad, is a mere 50 miles away. But the city is a border town in more ways than just where it’s located.

Culture

As the Washington Post explains, the majority of Kharkiv’s population is Russian-speaking. Residents here have particularly strong ties to Russia, with many traveling back and forth for commerce and family visits relatively recently. Now some say they resent conflict between the two countries and how inconvenient it’s made these trips.

Attitudes toward Russia are warmer in Kharkiv than elsewhere in Ukraine. Here, many Ukrainians also consider themselves Russian.

Kharkiv mayor Ihor Terekhov previously said residents respect Russia and love Ukraine.

“Yes, we speak Russian. If you ask me if Kharkiv citizens want Ukraine to be friends with Russia, the answer is definitely yes,” said Terekhov. “But do they want war? Definitely not. Do they want for us to be a piece of Russia? Of course not.”

On Feb. 5, thousands of Ukrainians marched through Kharkiv waving Ukraine flags and signs reading “Kharkiv is Ukraine.” Ukraine Pres. Volodymyr Zelensky previously said Kharkiv would be vulnerable to Russian attack. This image was reversed back in 2014, when pro-Russian separatists marched through the streets calling the city “Kharkiv People’s Republic.”

High tension

Russia-Ukraine relations have been tense since even before Ukraine gained independence and separated from the Soviet Union in 1991. The situation became even more tenuous in 2014, when pro-Russian Pres. Viktor Yanukovych was ousted after protests. Rather than leave the country, however, Yanukovych went to Kharkiv, where he and several other pro-Russia officials hoped to regain footing.

After the Ukrainian area of Crimea was seized by Russia in 2014, around half a million people who were displaced from the Donetsk and Luhansk regions relocated to Kharkiv. Since 2014 (and before), the city’s proximity has made pro-Russian protests – and even terror attacks – easier to stage.