The UK and its European neighbours confront two case studies, simultaneously, in how the continent is attempting, with varying degrees of success, to bind the United States into its future.
Firstly, there is Ukraine and then there is Greenland.
And all this at a time of deep scepticism in Washington about Europe: its importance, its outlook and its willingness to pull its weight to defend itself.
The futures of Ukraine and Greenland, both in the headlines at the same time, are the latest example of the mesmerising, head-spinning unpredictability of President Trump.
Privately, senior figures in London have a knowing look when the wild uncertainty of the White House crops up in conversation.
Every day is a rollercoaster, with little sense of where tomorrow or next week’s twist might take them, take us.
This week’s developments are particularly hard to read because outwardly they point in different directions.
Seven European leaders, including Sir Keir Starmer, issued a joint public statement emphasising, albeit in diplomatic language, their shared view that Washington’s designs on Greenland are as absurd as they are counterproductive.
We are on the same side, is the thrust of their message, and this is a waste of your energy because Greenland’s future is for Greenlanders to decide.
But they know too they should take President Trump seriously.
And then there is Ukraine. European diplomats believe they have persuaded America to commit to being a significant part of securing a long term peace in Ukraine – something Europe has long regarded as a prerequisite to a sustainable settlement for Kyiv, but which Washington has long resisted.
Now, sources tell me, they are cautiously optimistic they have the White House on board: the presence of President Trump’s envoys, Steve Witkoff and Jared Kushner, in Paris, at the gathering of what is known as the Coalition of the Willing was unprecedented and seen as a key indicator of a shift from Washington.
The accompanying document alongside the talks, while lacking in detail, spells out the anticipated role of America, and crucially, the UK and others.
The first component of what is described as “robust security guarantees for a solid and lasting peace in Ukraine” is a “US led ceasefire monitoring and verification mechanism”.
I am told this would make use of America’s advanced capabilities in what is described in military circles as “ISR” – intelligence, surveillance and reconnaissance. This means drones and satellites among other things. In other words: the advanced tools of modern warfare.
Precisely what America’s involvement could amount to, particularly if Ukraine was targeted by Russia again, isn’t clear but Ukraine and European capitals do see this latest development as a significant step forward.
Of course, a huge caveat remains: can peace be secured in the first place and would Ukraine be willing to give up on any of its territory? These are two massive and not yet answered questions.
Then, for the UK and others, there is the prospect of troops on the ground in Ukraine. That is a profound commitment, provoking its own big, unanswered questions: how many and for how long? Can this maintain popular support? And with what consequences for the military and for defence budgets?
Make no mistake this is a promise with implicit longevity attached: beyond this prime minister, beyond this government, beyond this American president.
That is what the reality of European security is expected to look like in the years, decades ahead.
“A secure Ukraine is a secure Europe and a secure Europe is a secure UK,” is how one Whitehall figure put it to me.
Expect that to be a key part of the message in the months to come.
Into the longer term, the UK and its neighbours will ponder how reliable or otherwise America will be: is the Trumpian era a blip or a waymarker towards an ongoing, unpredictable future?
Oh, and what will the White House be saying on Greenland and Ukraine next week, next month, next year?
