“The NRP Arpão became, if not the first, one of the very few conventional submarines to sail under the ice, an area normally reserved for nuclear-powered submarines. It remained under the ice sheet for a total of around four days, having also explored the operation in the Marginal Ice Zone, with a high density of loose ice, an area with high tacit value, an area in which no other Western submarine dared to operate, since World War II, with total success”.

The submarine 'Arpão' departed the Lisbon Naval Base on April 3, with 36 personnel on board, to participate in the Atlantic Alliance's 'Brilliant Shield' operation. On the occasion, the Chief of Staff of the Navy, Admiral Henrique Gouveia e Melo, highlighted the "high importance" of this mission as it is the first time that a Portuguese submarine will operate "under the Arctic ice".

The submarine returned to the surface “safely” on April 30 and the Navy emphasizes that this was “one of the greatest adventures” of this submarine to date.

In this operation, the Portuguese military had the support of the navies of the United States of America, Denmark, and Canada.