Prince William's first ever visit to Estonia comes at a critical time for global security. It will be highly symbolic given his role as the future Head of the Armed Forces.
Russia's offensive in Ukraine continues, despite President Trump's attempt to agree on a ceasefire, and Baltic nations are fearful they are next on Putin's hitlist.
The UK plays a crucial role in protecting its fellow NATO member, which insiders claim is already being targeted by Russia in acts of sabotage.
GPS jamming, stealing navigational equipment, and cyber-attacks are allegedly not uncommon, and the head of Estonia's Foreign Intelligence Service has urged counterparts to be "more aggressive" in response.
Prince William leaves England at critical time for global security
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The largest permanent deployment of British troops anywhere in the world right now is to Estonia - around 900 soldiers help guard NATO's eastern flank, close to the land border with Russia.
The North Atlantic Treaty Organisation's Article 5 states "an attack on one is an attack on all," so the UK's military presence in the region is designed to be a deterrent against Putin's aggression.
The Prince of Wales will be visiting British, Estonian and French personnel at the Tapa army base, the second member of the Royal Family to do so this year (Prince Edward visited in January.) It's further evidence the UK Government is keen to use the Royal Family to demonstrate soft power on the international stage.
As Colonel in Chief of the Mercian Regiment, His Royal Highness is expected to oversee a handover ceremony as the battlegroup takes over from the Royal Dragoon Guards (Prince Edward's regiment).
The former Prime Minister of Estonia Kaja Kallas being welcomed by Prime Minister Sir Keir Starmer last year
PAThe UK's role is codenamed "Operation CABRIT" and British troops lead Estonia's multinational battlegroup in NATO's Forward Presence - the other three battlegroups, led by other Western nations, are deployed to Latvia, Lithuania and Poland.
The battlegroups regularly take part in military training, and Prince William's own presence could give NATO forces added publicity in their battle readiness against threats from the East.
His Royal Highness is also meeting some of the estimated 60,000 Ukrainian refugees who fled to Estonia following Russia's invasion three years ago - that's the equivalent of three million refugees coming to the UK.
As a champion of mental well-being, the Prince is also visiting the Vabaduse Kool (Freedom School) in the country's capital, Tallinn, which was quickly built to continue Ukrainian children's education.
Many thousands were forced to leave their homes when the fighting started, and the Prince of Wales is thought to be keen to learn about how they have been supported to resettle in their new homes.
Prince William visiting Poland in support of Ukraine in 2023
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Sources close to the Prince also continue to dub him a "global statesman," and he will be meeting Estonia's President Alar Karis as soon as he arrives on Thursday.
Although Estonia is a former Soviet state, I get the impression it would rather be known as a small "tech-savvy" European nation. Since the fall of the Soviet Union in 1991, Estonia has become a thriving independent country - joining both the European Union and the Euro currency. It has the most business startups which have grown to be worth more than $1billion per head on the planet.
The country is believed to have welcomed Prime Minister Sir Keir Starmer's "reset" on Britain's relationship with the EU, and the Prince of Wales's diplomatic soft power could be a useful asset for the Labour Government's economic plans this week.
Estonians are thought to be big fans of the Royal Family, and are excited the Prince of Wales is visiting their country, but this is not an official State Visit.
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Princess Kate has also supported Ukraine throughout the war
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That responsibility is reserved for the King, but a positive reception could still help strengthen trading relations between Britain and Estonia.
I suspect His Royal Highness is particularly keen to see Estonia's backing for "clean tech" to combat climate change - he is attending an event to learn about renewable energy startups.
Perhaps this could inspire him to one day host his Earthshot Prize in the country - a 10-year plan to find, fund, and quickly scale up solutions to repair the planet.
As the future King of a constitutional monarchy, Prince William does not have free reign over what he can say or do. It is not up to him to dictate the UK's foreign policy, but his presence in a country bordering Russia will be highly significant.
President Trump, who has a deep respect for the Royal Family, is demanding other NATO allies invest more in defence - or he could withdraw US support.
The image of Prince William on the Eastern flank, surrounded by NATO troops from three independent nations, may remind the Western world that it is better to unite than to divide.
