In November, Russia gained a slice of somebody else’s country. It did this not through unidentified troops moving across a border, nor through hybrid warfare. Instead, it negotiated its capture in full view of, and without a single question asked by, the United States or the rest of the world.Fighting between Azerbaijan and Armenia over Nagorno-Karabakh preceded the annexation. The mountainous region is internationally recognized as part of Azerbaijan but since a 1994 ceasefire between the two nations has been controlled by ethnic Armenians. The conflict flared up again in September. Two months later came a peace deal, with Russia the winner: It mediated a ceasefire that placed the Kremlin’s ostensibly peacekeeping boots on the ground. America watched idly as this happened.As Armenia’s traditional protector, Russia held the only leverage to convince Armenia to sign this ceasefire. By signing, Yerevan gave up claims to the territories it had occupied within Azerbaijan since 1994 and gained nothing — bar a ceasefire rather than a forced surrender. In return for securing for its ally a marginally smaller humiliation, Moscow gained a present and a presence.In reality — unless America is prepared to engage fully in the peace process — Nagorno-Karabakh is now Russia’s indefinitely. The Kremlin ostensibly controls the territory for five years, with an automatic rollover for an additional five should none of the three parties to the ceasefire object six months before the end of the mandate.Russia certainly won’t. It is now gatekeeper to a region central to Europe’s energy diversification (reducing the role of Russian imports). If the region is strategically important to NATO, that makes it strategically important to the Kremlin.Armenia, for mistrust of Azerbaijan, will want the peacekeepers to stay. The short but brutal conflict has proven conclusively that Armenia cannot win militarily, and that therefore ethnic Armenians must accept either governance by Azerbaijan or the protectorate of Russia. Weak and broken, Yerevan finds it less of a humiliation to accept Russian tutelage in Nagorno-Karabakh, if only to deny an archenemy a complete victory. But this is a longer-term disaster for the Armenians. It means they are effectively trapped in a Russian embrace. They cannot turn west and cannot turn east — either diplomatically or for investment — because the Russians are now in charge.Though traditionally thought of by Moscow as “on the other side,” Azerbaijan — owing to lukewarm support from the United States and EU in recent years — has been steadily deepening diplomatic and economic relations with Russia, in part from necessity and a lack of serious alternatives. Yet now, with Russian military boots on Azerbaijani territory for the first time since the fall of the Soviet Union, Moscow’s leverage has also become economic leverage: By militarily guaranteeing a transport corridor across Armenia — closed before the ceasefire — to Azerbaijan’s exclave of Nakhichevan, Russia now controls Azerbaijan’s long-sought-after, direct land route from the Caspian Sea to the Mediterranean and Europe.The West certainly could have seen this coming. This is how it always begins: A toehold soon morphs into a footprint. Crimea, Eastern Ukraine, South Ossetia, Abkhazia — the list of examples goes on. Russian presence becomes Russian control: the only logic of Putin’s neo-czarist ambitions.Indeed, now, only a matter of weeks after troop deployment, the Kremlin is maneuvering: Lines on maps have started to bend and flex. On the Russian Ministry of Defense website, a page shows a map outlining the area where Russian peacekeepers, by the terms of the agreement, are to be stationed and will have jurisdiction within which to operate. On December 13, miraculously, the land they control had expanded. This was changed back to the original on the next day, after Azerbaijani diplomatic pressure. But this activity demonstrates that Kremlin cartographers are getting creative — and very early in this intervention.Rumors now swell of Russian “passportization” in Nagorno-Karabakh. Manufacturing new demographic realities on the ground by granting citizenship has been used to maintain influence in the internal affairs in other post-Soviet nations. Once Russians occupy the area, the Russian state is obliged to step in.It is a classic of the Kremlin repertoire. It preceded the invasion of Crimea. It happened in two regions in Georgia, South Ossetia and Abkhazia, again before wars broke out, with Russia coming out as the chief beneficiary. Most recently, passportization has been aggressively deployed in eastern Ukraine, through a helpfully streamlined process. The Kremlin forecasts that there will be over one million Russian citizens bearing newly minted documents by the end of the year. In all of these situations, Russia’s grip is secure.Passportization would mean that a negotiated settlement on the final status of Nagorno-Karabakh — what was supposed to be some form of autonomy within Azerbaijan, as in Soviet days — will never materialize. It will instead turn into a Russian-passport protectorate, giving Russia the pretext — or in Moscow’s lexicon, the legal right — to jump into the region were any imagined threat to its “citizens” to emerge.Considering the U.S.-led assistance now poured into Ukraine in the wake of Russian destabilization, it is surprising that more precautionary measures are not being taken in the South Caucasus.Yet time remains for America to step in: The ceasefire shall give way to negotiations for a final peace deal, with much left to decide. The U.S. must fully and comprehensively oppose passportization. American companies should invest in infrastructure and energy projects in the region so as to limit Russia’s room for maneuver. And U.S.-led joint investment initiatives between Armenia and Azerbaijan would help to cut the dependence of both on Russia.It’s time for America to step up diplomatic and economic efforts and reinsert itself in this process. Otherwise, Russia’s empire will continue to expand unchecked.