Exactly a month ago, the day after Athens and Skopje announced a breakthrough in talks on a name for the Former Yugoslav Republic of Macedonia, Foreign Minister Nikos Kotzias was in Moscow for talks with his counterpart, Sergei Lavrov.

In the two men’s statements there appeared to be no shadows over their countries’ relations.

“We noted our mutual interest in maintaining and substantially increasing the legacy left to us by our predecessors and the relations that have lasted for more than a century,” Lavrov declared.

If there was anything strange about this, it was his reference to a relatively short period of close ties, as Greeks and Russians have had friendly relations since long before the Russian Revolution.

Indeed, Kotzias noted that this year the two countries are commemorating 190 years of diplomatic ties.

Today, after Athens’s announcement that it was expelling two Russian diplomats and barring another two from entering, accusing them of illegal actions aimed at harming national security, this friendship is facing its greatest challenge since the two countries were on opposite sides in the Cold War.

The accusations suggest that there is much we do not know. According to Kathimerini’s report on Wednesday, the expulsions reveal underground tensions that have existed between Athens and Moscow for the past two years. Among the arguments for a resolution of the dispute with Skopje was that this would curb Moscow’s (and Ankara’s) influence in the region. Russia’s opposition to FYROM joining NATO was well known.

The Athens-Skopje deal opened the way for our neighbor’s accession (as long as both countries honor the agreement). In his statements with Kotzias, Lavrov had commented, “We have always emphasized that we stand for finding an agreement on this issue without outside interference and without establishing artificial terms and conditions.”

On Thursday, one day after NATO’s leaders issued an invitation to Skopje for the start of accession talks, the Russian Foreign Ministry protested against FYROM’s “forcible absorption by NATO.” Athens may hope that tension with Moscow will be limited, but the weight of the accusations against the four Russian diplomats and the expected tit-for-tat measures suggest a further worsening of relations.

The shadows must be cleared. It is imperative that the level of Russia’s influence in Greece’s politics, diplomacy, business, religious life and news media be the subject of thorough investigation.