I'm Russian. My family is Ukrainian. What happens if there's war?

To an ethnic Russian who came of age in the twilight of the Soviet Union, nothing feels more absurd than the idea of war between Russia and Ukraine.

Partly, that's personal. In the south of Russia, where I grew up, half of the people I knew had Ukrainian last names. My younger cousin's nickname was "little hen," because "Piven" meant "rooster" in Ukrainian. (Her father's family hailed from northern Ukraine.) As we dove for hermit crabs in the warm Black Sea or played Cossacks and bandits, I never thought of my cousins, whom I called "brother" and "sister," as Ukrainian. They were my family.

We in the south of Russia weren't just physically close to Ukraine — my grandmother was born in the Ukrainian city of Mariupol, just 70 miles away — we were culturally and linguistically intertwined. Ukrainian words ran through our southern dialect, and I can still sing a couple of Ukrainian folk songs. We also shared the same rich black soil: If Ukraine was the breadbasket of the Soviet Union, Kuban, the unofficial name of our region, was the granary of Russia.

Then there's our inextricably interwoven history. Both Russians and Ukrainians are descendants of Slavs, agricultural people wedged between Europe and the steppe. Both have suffered from the Mongol yoke, the czarist yoke and the Bolshevik yoke. After the collapse of the Soviet Union, the countries diverged. Yet the sense of a shared past was so strong that not even the Russian-backed conflict in eastern Ukraine could fully undo it.

Now the relationship between the two nations is at a breaking point. Around 130,000 Russian troops are stationed on the border, and war is a real prospect. Conflict between Ukraine and Russia would travesty centuries of commingling — like me, millions of Russians have Ukrainian relatives and vice versa — and draw to a bloody close the generative entwinement of cultures. It would be, quite simply, a tragedy.

Ukraine was a perennial presence in my childhood and adolescence. Staying with my grandparents in the summer, I would watch movies in the neoclassical white building of the Ukraina cinema in the center of town. At home we often had Ukrainian sirniki, or sweet cheese patties, for breakfast and Ukrainian borscht for dinner. During televised folk-dancing performances, intended to demonstrate unity between Soviet sister republics, I waited for the Ukrainian dancers. The women's colorful flower headdresses and spinning skirts were an embodiment of boldness and flair; I was entranced.

At school, the study of history began with Kyivan Rus, the confederation of Slavic principalities from the ninth to 13th centuries that spanned large parts of modern-day Belarus, Ukraine and European Russia. Kyiv, our textbooks serenely told us, was the "mother of Russian cities." In literature class, we memorized the description of the Dnieper River from "Taras Bulba," a novella by the Ukrainian-born giant of Russian letters, Nikolai Gogol. Later, after a longstanding ban was lifted, I devoured the novels of Mikhail Bulgakov, a native of Kyiv, where the vibrant thread of Ukrainian folklore was palpable. Then there were Ilya Ilf and Yevgeny Petrov, authors of the quintessential satirical novel, "The Twelve Chairs." Both hailed from Odessa, a port city on the Black Sea, in Ukraine.

The ineptness of that rule became horribly clear in 1986, when a nuclear reactor blew up in the Chernobyl power plant, about 80 miles north of Kyiv. Having sickened and displaced thousands, the disaster effectively ended the Soviet Union, setting off a series of reforms that led to its undoing. Since then, we've learned that participation in the Soviet experiment wasn't quite voluntary — and that for Ukraine, the cost included Holodomor, a famine created by Stalin's collectivization plan that claimed the lives of nearly four million Ukrainians in the early 1930s.

The breakup of the Soviet Union, which I lived through, was no catastrophe for relations between the two countries. It felt more like a divorce in which the parents decide to stay friends for the sake of the children. Ukraine, for one, allowed Russia to keep its major naval base in Sevastopol in Crimea and gave up its nuclear arsenal. Cultural and social ties endured. During summers in the early '90s, I worked as a counselor in a youth camp on the Black Sea: Most of the children were from Donetsk, the Ukrainian coal-mining region. "U-kra-i-na, I love you!" we screamed at the top of our lungs during soccer matches and dance competitions.

Not that the relationship between Russians and Ukrainians was harmonious, of course. Who likes their evermore heroic "elder brother," as Russians were positioned in the Soviet Union? On paper, national cultures were celebrated, as were national languages. But to achieve anything at the top level, in singing or mathematics or anything else, you had to go to a leading university in Moscow, speak Russian and, in general, be Russian enough. Public expressions of national feeling risked being branded nationalistic.

You also had to put up with commonplace Great Russian chauvinism, a term coined by Lenin to describe one of the unfortunate ways a historically oppressed people found self-affirmation. Most non-Russian nationalities found themselves the butt of jokes. (Ukrainians were portrayed as lard-obsessed nationalists, for example.) That bred resentment, particularly in areas that had been historically and culturally closer to Europe, like western Ukraine and the Baltic republics. I remember trying to get help after missing my train in Tallinn, Estonia, in the early 1990s and getting nowhere until I switched from Russian to English.

That resentment faded once the grounds for it were removed. In the late 1990s and early 2000s, Russia and Ukraine, two sovereign states, watched each other from a distance, busy building their future. Awash with oil money, Russia did indisputably better economically; plenty of Ukrainians went to look for work in Moscow. Yet it also grew more authoritarian and isolationist, while Ukraine, for all its difficulties, seemed to be committed to a pro-Western, democratic path. When, in 2013 and 2014, Ukrainians rallied against a president who opposed integration with the European Union, I rooted for them from afar.

Now it's not just eastern Ukraine menaced by Russian aggression but the entire country. After months of speculation, shuttle diplomacy and threats, Ukraine stands on the brink of war. It wouldn't be the first victim of post-Soviet expansionism. Georgia, Moldova and Chechnya were all sucked into a military conflict with their former elder sibling, with predictable results: Russia won, they lost.

But a war with Ukraine would be different and not just because it has a fratricidal feel to it. Ukrainians, who sacrificed millions of lives to save the Soviet Union from the Nazis, are masters of partisan resistance. The conflict would be protracted, the victory pyrrhic and the consequences for Russia as a nation disastrous. "Rus, whither are you speeding to?" Gogol writes in "Dead Souls." It's a good question.