Koivisto, who served as President of Finland from 1982 to 1994, sent support to Estonia covertly, disguised as funding for cultural cooperation work, so as not to draw ire from Moscow, reported Finnish public broadcaster Yle.

In 1991, he publicly declared that Finland could not interfere in the internal affairs of the Soviet Union, however at that point, Finland had already decided a few years prior to help Estonia. "Estonia had declared sovereignty, and Finland's close circles had decided to support Estonian independence as much as possible," wrote Yle.

This lack of public support by the former Finnish president for their southern neighbor was unpopular among Finns. "'He did this in public because he thought that it was in Finland's best interests to maintain a good relationship with Moscow,' says historian and researcher Heikki Rausmaa, who defended a doctoral dissertation on Finland's aid to Estonia in 2013."

According to Rausmaa's research, however, by 1991, Finland had contributed over 100 million Finnish marks, or over €16 million, toward Estonian independence. "In addition to this material support, Finland provided expert consultation and training to its southern neighbor, which basically had to build a market economy and system of democractic rule from scratch," Yle wrote.

Finland's approach involved sending money to Estonia under the guise of funding for cultural cooperation. "[Minister of Education and Culture Anna-Liisa] Kasurinen reportedly asked Koivisto how much help Finland could give to Estonia, to which Koivisto replied, 'Well, you can practice a lot of things in the name of culture,'" wrote Yle.

The Tuglas Society and the Finnish-Estonian Cultural Association, where future Estonian President Lennart Meri was working when news reached Finland of Estonia's successful bid to formally restore its independence on Aug. 20, 1991, were two organizations to receive financial support from Finland.

Nonetheless, Koivisto chose to remain quiet about this support, even to the partial detriment of his level of public support in the early 1990s. In a rare instance, just one month after Estonia had re-estabished its independence, Koivisto said in an interview with Estonia's public broadcaster, "'It is not general knowledge in Estonia — and it never will be — all the things that Finland has done for Estonia.'"

Koivisto, who had also served as Finnish Prime Minister, Minister of Finance and Chairman of the Board of the Bank of Finland, died in Helsinki on May 12, aged 93.