Russian armoured vehicles sail after submerging from an amphibious assault ship during the Navy Day parade in the Black Sea port of Sevastopol, Crimea July 28, 2019. REUTERS/Alexey Pavlishak

Russian armoured personnel carriers sail after submerging from an amphibious assault ship during a rehearsal for the Navy Day parade in the Black Sea port of Sevastopol, Crimea July 26, 2019. REUTERS/Alexey Pavlishak

Russian armoured personnel carriers submerge from an amphibious assault ship during a rehearsal for the Navy Day parade in the Black Sea port of Sevastopol, Crimea July 26, 2019. REUTERS/Alexey Pavlishak

An MH-60S Sea Hawk is fastened down after it was landed on the flight deck of the U.S. Navy amphibious assault ship USS Boxer, near a Light Marine Air Defense Integrated System (LMADIS) counter-unmanned aircraft system mounted on a vehicle parked at the bow, in the Arabian Sea off Oman July 16, 2019. Picture taken July 16, 2019. REUTERS/Ahmed Jadallah

REFILE- REMOVING AND ADDING INFORMATION An MH-60S Sea Hawk is seen after it was landed on the flight deck of the U.S. Navy amphibious assault ship USS Boxer, near a Light Marine Air Defense Integrated System (LMADIS) counter-unmanned aircraft system mounted on a vehicle parked at the bow, in the Arabian Sea off Oman July 16, 2019. Picture taken July 16, 2019. REUTERS/Ahmed Jadallah

Spanish Army servicemen walk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

Spanish Army servicemen talk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

Spanish Army servicemen talk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

Spanish Army servicemen walk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

Spanish Army servicemen walk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

Spanish Army servicemen talk after amphibious landing from assault ship-aircraft carrier LHD Juan Carlos I during Baltops 2019 NATO military exercise in Lilaste, Latvia June 12, 2019. REUTERS/Ints Kalnins

An amphibious assault ship and armored personnel carriers are seen during military exercises, which are staged by the Baltic Fleet forces of the Russian Navy to train amphibious assault, at Khmelevka firing ground on the Baltic Sea coast in Kaliningrad Region, Russia April 4, 2019. REUTERS/Vitaly Nevar

BTR-82A armored personnel carriers submerge from an amphibious assault ship during military exercises, which are staged by the Baltic Fleet forces of the Russian Navy to train amphibious assault, at Khmelevka firing ground on the Baltic Sea coast in Kaliningrad Region, Russia April 4, 2019. REUTERS/Vitaly Nevar

An amphibious assault ship and armored personnel carriers are seen during military exercises, which are staged by the Baltic Fleet forces of the Russian Navy to train amphibious assault, at Khmelevka firing ground on the Baltic Sea coast in Kaliningrad Region, Russia April 4, 2019. REUTERS/Vitaly Nevar

An amphibious assault ship, armored personnel carriers and helicopters are seen during military exercises, which are staged by the Baltic Fleet forces of the Russian Navy to train amphibious assault, at Khmelevka firing ground on the Baltic Sea coast in Kaliningrad Region, Russia April 4, 2019. REUTERS/Vitaly Nevar

A BTR-82A armored personnel carrier submerges from an amphibious assault ship during military exercises, which are staged by the Baltic Fleet forces of the Russian Navy to train amphibious assault, at Khmelevka firing ground on the Baltic Sea coast in Kaliningrad Region, Russia April 4, 2019. REUTERS/Vitaly Nevar

A Union Jack flag is seen from the bridge of HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Commanding Officer Captain Tim Neild RN of HMS Albion, the British Royal Navy flagship amphibious assault ship, is seen upon the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Commanding Officer Captain Tim Neild RN of HMS Albion, the British Royal Navy flagship amphibious assault ship, takes the captain's seat during an interview with Reuters after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Commanding Officer Captain Tim Neild RN of HMS Albion, the British Royal Navy flagship amphibious assault ship, speaks during an interview with Reuters after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Crew members of the HMS Albion, the British Royal Navy flagship amphibious assault ship, are seen upon the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Crew members of the HMS Albion, the British Royal Navy flagship amphibious assault ship, are seen upon the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Viking amphibious armored vehicles are seen on the flight deck of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Crew members of the HMS Albion, the British Royal Navy flagship amphibious assault ship, walk in front of Viking amphibious armored vehicles after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Crew members of the HMS Albion, the British Royal Navy flagship amphibious assault ship, are seen in front of Viking amphibious armored vehicles after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

HMS Albion, the British Royal Navy flagship amphibious assault ship, arrives at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Command and Control centre of HMS Albion, the British Royal Navy flagship amphibious assault ship, is seen after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Command and Control centre of HMS Albion, the British Royal Navy flagship amphibious assault ship, is seen after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Hippo beach recovery vehicle is seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Military vehicles are seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Viking amphibious armored vehicles are seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Viking amphibious armored vehicles are seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Military vehicles are seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

Military vehicles are seen in the loading dock of the HMS Albion, the British Royal Navy flagship amphibious assault ship, after the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

A crew member of the HMS Albion, the British Royal Navy flagship amphibious assault ship, is seen upon the ship's arrival at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

HMS Albion, the British Royal Navy flagship amphibious assault ship, arrives at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

HMS Albion, a British Royal Navy amphibious assault ship, arrives at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

HMS Albion, a British Royal Navy amphibious assault ship, arrives at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

HMS Albion, a British Royal Navy amphibious assault ship, arrives at Harumi Pier in Tokyo, Japan August 3, 2018. REUTERS/Toru Hanai

USS Wasp amphibious assault carrier sails as a U.S. Marine Corps MV-22 Osprey aircraft flies near the ship during their operation in the waters off Japan's southernmost island of Okinawa March 23, 2018. REUTERS/Issei Kato

French Prime Minister Edouard Philippe (C) speaks with officials as he visits the French BPC Mistral amphibious assault ship with French Defence Minister Florence Parly at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe stands at attention as he visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe, flanked by French Defence Minister Florence Parly, addresses French sailors as he visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe speaks with French sailors as he visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe visits the French BPC Mistral amphibious assault ship with French Defence Minister Florence Parly (R) at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe watches a helicopter land on deck as he visits the French BPC Mistral amphibious assault ship with French Defence Minister Florence Parly (2ndR) at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe walks with officials as he visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe (C) visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe (2ndR) visits the French BPC Mistral amphibious assault ship at sea off Toulon, France September 30, 2017. REUTERS/Franck Pennant/Pool

French Prime Minister Edouard Philippe walks with officials as he visits the French BPC Mistral amphibious assault ship at sea off Toulon, France, September 30, 2017, during a one-day trip to the French navy base. REUTERS/Franck Pennant/Pool

The "Juan Carlos I" amphibious assault ship from the Spanish Navy sails during an international aerial and naval military exhibition commemorating the centennial of the Spanish Naval Aviation, over a beach near the naval airbase in Rota, southern Spain, September 16, 2017. REUTERS/Jon Nazca

A Sikorsky SH-3 Sea King rescue helicopter from the Spanish Navy fly while the ""Juan Carlos I" amphibious assault ship sails during an international aerial and naval military exhibition commemorating the centennial of the Spanish Naval Aviation, over a beach near the naval airbase in Rota, southern Spain, September 16, 2017. REUTERS/Jon Nazca

The "Juan Carlos I" amphibious assault ship from the Spanish Navy sails during an international aerial and naval military exhibition commemorating the centennial of the Spanish Naval Aviation, over a beach near the naval airbase in Rota, southern Spain, September 16, 2017. REUTERS/Jon Nazca

An AV-8B Harrier jet takes off from the Spanish Navy "Juan Carlos I" amphibious assault ship during an international aerial and naval military exhibition commemorating the centennial of the Spanish Naval Aviation, over a beach near the naval airbase in Rota, southern Spain, September 16, 2017. REUTERS/Jon Nazca

A U.S. Marines MV-22 Osprey Aircraft flies over a jet before landing on the deck of the USS Bonhomme Richard amphibious assault ship off the coast of Sydney, Australia June 29, 2017. Picture taken June 29, 2017. REUTERS/Jason Reed

A U.S. Marines MV-22 Osprey Aircraft flies over a jet before landing on the deck of the USS Bonhomme Richard amphibious assault ship off the coast of Sydney, Australia June 29, 2017. Picture taken June 29, 2017. REUTERS/Jason Reed

Journalists and officials board a U.S. Marines MV-22B Osprey Aircraft on the deck of the USS Bonhomme Richard amphibious assault ship off the coast of Sydney, Australia June 29, 2017. Picture taken June 29, 2017. REUTERS/Jason Reed

A U.S. Marines MV-22 Osprey Aircraft lands on the deck of the USS Bonhomme Richard amphibious assault ship off the coast of Sydney, Australia June 29, 2017. Picture taken June 29, 2017. REUTERS/Jason Reed

Journalists and officials fly aboard a U.S. Marines MV-22 Osprey Aircraft from the deck of the USS Bonhomme Richard amphibious assault ship off the coast of Sydney, Australia June 29, 2017. Picture taken June 29, 2017. REUTERS/Jason Reed