Two years on from being annexed from the rest of Ukraine by Russian forces, tensions between Moscow and Kyiv over Crimea are rising again.
The latest round of worries have been sparked by accusations of Ukrainian incursions into the Crimean peninsula.
Russia's foreign ministry said that the alleged death of servicemen last weekend during clashes would have consequences, Reuters reported, though Ukraine has denied that the skirmishes took place.
The latest row has prompted analysts to take a fresh look at the problems surrounding Crimea and why relations are under strain again.
Using a fresh piece of analysis from Timothy Ash, head of emerging-market strategy at Nomura International, CNBC take a look at six reasons: