What is the referendum about?

The two million inhabitants of Crimea had to decide whether they want to belong to Russia, or whether they want to continue to be part of Ukraine. Under international law, the Crimea belongs to Ukraine, but it holds the status of an autonomous republic with its own parliament, which voted at the beginning of March to become part of the Russian Federation. The head of the parliament, Vladimir Konstantinov, has already sent a request to Russian President Vladimir Putin. The referendum is designed to legitimize the step.

Why does Crimea belong to Ukraine in the first place?

In 1954, on the 300th anniversary of unification of Russia and Ukraine, Soviet leader Nikita Khrushchev - himself a Ukrainian - declared the peninsula a part of the Ukrainian Soviet Socialist Republic. In 1992, only a year after Ukraine's declaration of independence, a referendum was already on the question of Crimea's future. This - initiated by pro-Russian forces - was blocked by the government in Kyiv. In response, the Crimeans established an autonomous republic with far-reaching powers. The town of Sevastopol would be administered from Kyiv - though as a naval base for its Black Sea fleet, the town is also of major importance for Russia.

The Crimea is strategically significant to Russia's navy

Why is Crimea so important?

The peninsula has been a bone of contention between Russia and Ukraine for centuries, because of its strategically desirable position on the Black Sea coast. In the first half of the 19th century, Russia built up Sevastopol, Crimea's largest city, to be the main base for its Black Sea fleet. Following the October Revolution of 1917, Crimea became an autonomous republic of the Soviet Union.

Following the occupation of Crimea by the Wehrmacht, Germany's armed forces, during the Second World War, Russian leader Joseph Stalin deported the peninsula's entire original population - the so-called Crimean Tatars - to Central Asia, in order for Russians to colonize strategically important areas. The few Tatar survivors were only allowed to return in 1988. Today they represent about 12 percent of the population, alongside 60 percent Russians and only 24 percent Ukrainians.

What are the differing positions on Crimea's independence?

The pro-Russian majority of the Crimean population wants to join the Russian Federation as quickly as possible. Crimea's Ukrainians and Tatars are in favor of an independent Crimea within Ukraine - in other words, maintaining the status quo.

The Crimeans have been staging both pro- and anti-Ukrainian protests

What do experts on international law make of the referendum?

Western experts agree that both the Crimean parliament's vote and the imminent referendum on the region entering the Russian Federation are not binding under international law. Although the Ukrainian constitution does allow local referendums on political questions, alterations to Ukraine's borders require national referendums. In other words, only the entire Ukrainian population can legally decide whether Crimea should join Russia.

Although a people does have the right to self-determination in principle, a small group within a people can only claim that right in exceptional circumstances. Despite the many political tensions currently mounting in the region, the inhabitants of Crimea have not reached that stage - yet.

On top of this, the right to claim secession is annulled if another state intervenes externally, which Russia has clearly done. Moscow's argument, that it is only intervening in the conflict to protect the Russian section of the population, is not legitimate, legal experts say. The deployment of Russian soldiers in Sevastopol is a clear violation of international law. The United Nations Charter bans the threat or the use of violence against a territory or the political independence of another state.

Why is the Crimean referendum important to the West?

Ukraine and the European Union drew up an agreement a few months ago aimed at improving ties. Under pressure from Moscow, the now fallen Ukrainian President Viktor Yanukovych declined to sign the deal at the last minute, and instead negotiated a billion-dollar deal with Russia that was meant, among other things, to guarantee cheaper gas deliveries.

Crimea has been a bone of contention for centuries

The West does not want Moscow to expand its influence in the region. If Crimea joins the Russia Federation, the Kremlin might then increase economic pressure on Ukraine, since Yanukovych's gas deal would be void.

Should Western countries decide to impose sanctions on Russia, the Kremlin could find itself in a tricky position economically. On the other hand, many European countries are dependent on Russian gas and oil deliveries. The consequences for individual countries are hard to predict, but there would certainly be significant costs associated with putting sanctions in place against Moscow.

What would happen after the referendum?

Should the majority of Crimeans vote to join the Russian Federation this Sunday (16.03.14), as expected, the self-proclaimed leadership of Crimea would repeat its request to the Kremlin. The Russian parliament, the Duma, would then have to pass a special law in order to allow Crimea in. The upper chamber of the Russian parliament, the Federation Council, has already signaled its agreement. The final decision would still be made by Putin.

Russia's deployment on the peninsula is illegal, say experts

The citizens of Crimea would then be issued their own passports, but would presumably also be allowed to keep their own Ukrainian IDs. The official languages of Crimea would become Russian and Tatar - Ukrainian would be scrapped.

Ukrainewould then have to withdraw its soldiers from the peninsula. Those troops that have sworn an oath to the pro-Western government in Kyiv would either have to defect or leave, Deputy Prime Minister Rustam Temirgaliyev has declared. He said he does "not want to see a Ukrainian uniform on Russian Crimea."

A Ukrainian military intervention aimed at trying to re-conquer the peninsula following the referendum would be legitimate, some international legal experts say. But the 200,000 Ukrainian troops would barely stand a chance against the Russian army, the third-largest in the world with one million regular troops and 1.5 million reserves. Ukraine could not count on any support from the West either, since military intervention would be much too dangerous.