Nato member states operating in the Baltic Sea have considerably improved their reaction time in responding to suspicious vessels since launching the operation Baltic Sentry earlier this year.
"Previously, it would take us around 17 hours to respond. Now the response time has dropped to less than an hour," said Commodore Marko Laaksonen, Deputy Chief of Staff for Operations in the Finnish Navy.
Nato increased its presence in the Baltic Sea in January after repeated damage to critical underwater infrastructure.
The vessels suspected of committing the damage have been linked to Russia's shadow fleet, vessels that are typically over 15 years old, poorly insured and are often involved in deceptive maritime practices and sanctions evasion.
The role of the shadow fleet in damaging critical infrastructure has not yet been proven.
Many of the vessels in the shadow fleet sail out of the Baltic Sea before they can be questioned by local authorities.
One of the ships suspected of damaging critical infrastructure in the Baltic Sea was the Eagle S, which Finland detained up until last month.
Since the end of February, a detachment from the US Marine Corps has been based in Finland and participating in the operation.
The Marines have been tasked with monitoring the maritime environment, critical infrastructure and movements of vessels in the Baltic Sea.
"They can send their drones where needed and we then get confirmation of what kind of vessel is in the Gulf of Finland and what it is doing," Laaksonen told Yle.
According to Laaksonen, several aspects are taken into account in the mapping and risk assessment of Russian shadow fleet vessels. The owner, crew, route and history of the vessel must be established.
"Using this information, we can determine whether or not a ship could be a threat," Laaksonen said.
For the ships in question, Nato will make their presence known.
"We'll get close by, and then contact them, for example, over the radio and ask them their destination and intentions. At least they know they are being watched and if something specific happens, it will be dealt with," Laaksonen said.
Nato solidifies presence in the Baltic
According to Laaksonen, in the last three months Finland has detected a few hundred vessels from the shadow fleet in its vicinity.
The ships can be identified by their poor condition and crews unfamiliar with sailing in the Baltic.
Oil tankers in poor condition are also a considerable risk for the environment.
Laaksonen could not yet say whether the Baltic Sentry monitoring operation will continue into the future. However, he said that Nato will remain in the Baltic Sea area.
"Nato's presence will be maintained in the Baltic Sea, either through permanent naval units or through the ships of Nato member states. We will continue to monitor the shadow fleet and protect critical infrastructure on our side," Laaksonen said.
Finnish conscripts in a class of their own
US Marine Corps Captain Adan Galindo said that cooperation with the Finnish Navy has been seamless.
"It's been fairly easy to integrate with them, share some of our tactics, techniques, procedures and really understand how they operate. And just be able to put to the test, if something were to actually happen, how well would we be able to integrate together," Galindo said.
According to Corporal Aaro Härkönen, who is doing his military service in the Upinniemi Coastal Brigade, the US Marines have been satisfied with the performance of the Finnish conscripts.
"They have found us to be a competent group and everything has worked out very well," Härkönen said.
It has come as a surprise to Härkönen's comrade Corporal Lenni Mattila how much the Americans really value Finnish conscripts.
"They sometimes compared us to the Norwegian conscripts, that we were a completely different class. In that sense we can be satisfied," Mattila said.
