hen the Finnish Reservists’ Assn. recently announced wartime defense courses for civilian women in the southern town of Haemeenlinna, the 400 slots filled almost immediately, with a waiting list of 500 more.

Topics will include shooting, cybersecurity and how to manage the first several days of an invasion from abroad.

“I wouldn’t call it fear,” said Sgt. Sonja Airikki, a 39-year-old reservist who will lead the training next month. “It’s more about being prepared.”

Military readiness is ingrained in the culture of this country of 5.5 million people that shares an 833-mile border and a long, complicated history with Russia.

The relationship has grown increasingly tense since Russia invaded Ukraine two months ago. For the first time, Finland is considering seeking membership in NATO, prompting threats of retaliation from Russian President Vladimir Putin.

The reservists group is primarily responsible for keeping its call-up soldiers ready for war. Its civilian classes — like those Airikki leads — have always been popular, but nothing prepared it for the nationwide enrollment spike since the attack on Ukraine.

“The change has been enormous,” said Ilpo Pohjola, a top official with the association who has been with it since its inception almost 30 years ago. “It’s something very special. I haven’t seen anything like this before.

“We have known for 100 years that there is evil on the opposite side of the border, but now I think people have woken up,” he said. “They understand that we must be prepared.”

Wariness of Russia dates back to 1809, when Russia added Finland to its empire after winning it in a war with Sweden. Finland declared independence in 1917, while Russia was distracted by revolution, but 22 years later the Soviets invaded.

The Finnish army was vastly outnumbered, but using snipers to terrorize enemy soldiers in the frozen forests and Molotov cocktails — its own invention — to attack their tanks, it fended off the Soviets in two separate wars....