A cease-fire has been called in embattled Ukraine, one that many world leaders are skeptical will last. Yet even as the fighting that had flared along Ukraine's strategic southeastern coast Thursday fell silent in the hours after the cease-fire was announced, larger questions about the territory of Ukraine remain, as does a vow from separatists to split from Ukraine entirely.

The details of the cease-fire, signed in Minsk by negotiators representing the Ukrainian government, the separatists, Russia, and the Organization for Security and Cooperation in Europe, include amnesty for fighters who disarm and have not committed serious crimes, the disbanding of militias, the release of hostages, and a ten-kilometer buffer zone to be created along the Russian-Ukrainian border, according to news reports. The deal states that power would be decentralized—with an appointed governor to be granted control of provinces—and also includes provisions regarding the protection of the Russian language and early elections.

But realities on the ground may be different, Russian news agencies report. Igor Plotnitsky, one of the rebel leaders of the self-proclaimed Luhansk People's Republic, says, "The cease-fire does not mean a shift from our course of breaking away from Ukraine. This is a compulsory measure."

The agreement, say experts, already signals Ukraine's weakness and potential loss of territory.

"This is definitely a loss for Ukraine," says Faith Hillis, assistant professor of Russian history at the University of Chicago and author of Children of Rus': Right-Bank Ukraine and the Invention of a Russian Nation. She says the first question is whether the cease-fire will hold, but "this looks as if Ukraine will lose parts of the east, whether through a federalization scheme or some sort of autonomy reached for the region. Parts of Ukraine could end up as a 'frozen conflict.' " If so, they would join several other post-Soviet regions with unresolved political status, like South Ossetia, Abkhazia, or Transdniestria, the breakaway state located between the Dniester River and Moldova's eastern border with Ukraine.

Recent pro-Russian territorial gains included strategic territory that could hasten the forging of a land bridge to the geographically isolated Crimea, the Black Sea peninsula that Russia annexed in the hastily called referendum last March, all the while occupying prized coastline along the way. The most recent fighting was centered around the southeastern port city of Mariupol on the Sea of Azov, with its potential oil and gas reserves. In nearby Novoazovsk, flags of the so-called Novorossiya (New Russia) Army were already flying.

View Images Juan José Valdés, Lauren James, NG Staff. Sources: Information and Analysis Center of the National Security and Defence Council of Ukraine; All-Ukraine Population Census 2001, State Statistics Committee of Ukraine; OpenStreetMap; GADM; Portnews

View Images The Kerch Strait separates Crimea from Russia and demarcates the Sea of Azov from the Black Sea. Hitler once tried to build a bridge across the 2.5-mile-wide expanse, but the Nazis were foiled by the advancing Red Army. Putin has called for a new rail and road bridge there. Photograph by Serguei Fomine, Russian Look/Corbis

New Russia

The term Novorossiya itself carries an implication of aggression, harkening back to an era of Russian imperial expansion in present-day southern Ukraine, when vast swaths of the region were won from the Ottoman Empire by Catherine the Great and ruled from up north.

But however one chooses to label the land, having a foothold there—either through continued fighting or as a result of frozen gains due to a cease-fire—is a crucial link to Crimea.

"There is a supply issue," says Professor Hillis. "Crimea was part of Ukraine since 1954, and its food, energy, and water supply was all piped in from mainland Ukraine."

By taking the region, pro-Russian entities would have an easier time transporting supplies to Crimea because they would control the mainland closest to the peninsula.

View Images Ukrainian soldiers ride on a tank in the port city of Mariupol, in southeastern Ukraine. A ceasefire in the embattled areas of eastern and southwestern Ukraine was declared Friday. Photograph by Sergei Grits, AP

Putin's Plan?

The second thing Putin is after "is the historical notion of New Russia. Putin is bringing this up now not only as a way to create a connection to Crimea," Hillis says, but also "to leave the Ukrainian state divided and fractured and to create a psychological impact as well."

The pro-Russian forces that had pushed along the coast of Ukraine, however, are just the latest in a line of invaders, occupiers, and settlers from ancient times to the present who have tried to occupy this strategic stretch.

View Images A Ukrainian soldier rests as he patrols territory close to a Ukrainian checkpoint near the town of Gorlovka. Fighting was reportedly still ongoing in the city of Mariupol hours after a ceasefire was declared Friday. Photograph by Roman Pilipey, EPA/Corbis

The Wild Fields

For centuries it was a no-man's-land. "They called it the Wild Fields," says Charles King, professor of international affairs and government at Georgetown University in Washington, D.C., and author of The Black Sea: A History.

"The Wild Fields was a term used for a good part of all the area north of Crimea," he says. "This was a term used by Slavs, in the era before the large-scale colonization of the 18th century, because it was a kind of buffer between the Muscovite princes in the north and the Tatars in Crimea, who were in league with, and notionally subservient to, the Ottoman sultans. And in between them was this kind of vast cordon of steppeland or what we would call prairie."

It was also "flat and easy to conquer," adds the University of Chicago's Hillis. "It was raided by the Mongols in the 13th century and very badly depopulated. As a result, after that it was a borderland for many centuries between the Russian Empire and the Ottoman Empire."

The area was called the Wild Fields "essentially because it was, well, a big field," she explains. "But also because it was populated by a ragtag group of settlers who would escape various regimes and settle there, and also by Cossacks who were mercenaries serving various states. The region had this mythology around it as this place of freedom and lawlessness, the borderland of empires."

By the 18th century, however, Russia had won much of the territory—including Crimea—for itself, and the term "Wild Field" was largely replaced with "Novorossiya."

''New Russia was Russia's answer to overseas colonialism at roughly the same time," says King. "But what began in the late 18th century as a form of colonialism—inviting in colonists to settle a region that had been traversed by Tatars and nomads loyal to the Ottoman Empire—became over time a province of the wider empire." Colonists included Germans, Czechs, Greeks, Armenians, "you name it," says King.

But controlling the southern coastal territory isn't the only way to access Crimea from mainland Russia.

View Images Planes of the German Luftwaffe fly over the Sea of Azov during World War II. The Nazis tried to build a bridge over the Kerch Strait but only got so far before the Russians advanced on Crimea in 1944. Photograph from Keystone-France/Gamma-Keystone via Getty Images

Hitler's Bridge

During World War II, Adolf Hitler commissioned a bridge to cross the Kerch Strait, which separates Crimea from Russia and demarcates the Sea of Azov from the Black Sea, at its narrowest point.

"Hitler saw Crimea and Ukraine as a new place where the German peasantry could renew itself. It would be Germany's breadbasket," says Harry Bennett, a professor of history at Plymouth University in the U.K. and author of The Nazi, the Painter and the Forgotten Story of the SS Road. A bridge would also allow the German 17th Army to get thousands of tons of supplies along southern routes deeper into the mainland.

But the Nazis only got so far before the Russians advanced on Crimea in 1944. "When the Russians got there, they found a partially built bridge and all the tools to finish it," says Bennett. "The irony is that Hitler's bridge, instead of moving German troops into the heart of Asia, helped bring Russian troops to Berlin."

But the winter and the icy strait took their toll on the hastily finished bridge, says Bennett. "Sections of the bridge just dropped off into the Kerch Strait and the bridge was abandoned."

View Images Armed militiamen from the pro-Russian Donetsk People's Republic pose proudly during Ninth of May celebrations in the eastern Ukrainian city of Donetsk. The separatist forces are party to a ceasefire signed Friday in the Belarusian city of Minsk. Photograph by Janos Chiala, NurPhoto/Corbis

"A Path to Russia"

Now Putin must figure out how to traverse the strait. Earlier this year, the day after Crimea was officially annexed, Putin called for a new rail and road bridge. Speaking from Crimea's port city of Sevastopol, Gennady Basov, head of the Russian Bloc political party, says his people would support any pro-Russian forces or plans that would forge a link to the mainland—whether from Ukraine's coast or from Russian territory.

"What people are saying about Russian troops crossing into Ukraine is something only an American could believe," says Basov. "The fighters are volunteers, fighting for their own land. If they were to make it all the way to Crimea, we would welcome that."

As for a bridge linking Crimea to the mainland, Basov tells National Geographic: "Kerch—yes, it's planned. Crimchani [Crimeans] want it. We want free access and a path to Russia."

View Images Despite the advance of both pro-Russian and Ukrainian troops, locals in the Ukrainian city of Mariupol take to the beaches to enjoy the good weather. Photograph by Alexander Ermochenko, EPA/Corbis