Britain has special forces deployed to Ukraine in an advisory role who sometimes find themselves “very close to the front lines”:
Still, three Western government sources tell me that Ukraine's deep battlespace effort owes especial thanks to Britain — specifically to British strike and reconnaissance special forces personnel inside Ukraine. This UK deployment was originally supervised by the now-retired head of the British Army, Gen. Mark Carleton-Smith, a former head of the U.K. Special Forces command who is deeply respected by the Army's combat infantry cadres.
I am told that this military advisory effort is being supervised by the United Kingdom's foreign intelligence agency, the Secret Intelligence Service, also known as MI6. While other Western nations also have a special operations forces presence inside Ukraine (to include CIA paramilitary and operations officers), Britain has adopted a particularly forward-leaning approach to supporting Ukraine.
This reflects a personal and professional assessment by Prime Minister Boris Johnson and the U.K. national security establishment in favor of highly active support for Ukraine. Foreign Secretary Liz Truss, the heavy favorite to replace Johnson as prime minister on Sept. 6, appears set to continue this effort.
That said, the U.K.'s activity here is highly significant. It has, at times, involved advisory U.K. special forces activity very close to the front lines. (I understand that U.K. forces are not authorized to directly engage Russian forces.) Regardless, Ukraine's escalating deep battlespace campaign is a direct extension of long-standing British special forces doctrine.
Whatever the details, having British commandos advising Ukrainians in Ukraine probably reaches and exceeds the threshold of war.
That said, Western involvement already exceeds the threshold of war without the advisory missions on the ground. Flying surveillance aircraft and collecting electronic chatter, sharing satellite images, refurbishing and repairing Ukrainian tanks, and making a present of weapons and money to Ukraine are not neutral acts. Nor are the sanctions (economic & financial warfare). — That said, Russia is in no position to protest since Russia hasn’t even declared war on Ukraine.
If a country is formally at war, it can by international law demand that 3rd countries refrain from non-neutral acts (only trading with the belligerents in a non-prejudicial manner in goods other than weapons is permitted), or else they will not enjoy the protection of neutral status.
But since Moscow maintains it is not at war in Ukraine, or with Ukraine, that falls by the wayside.
The Orwellian “special military operation” is not a recognized term in international law. Moscow proclaims itself to be pursuing a vague “SMO” on Ukraine’s territory but that obligations nobody else to nothing.
Legally, that Russia is pursuing an “SMO” inside Ukraine is of no consequence to US or Britain. Since Moscow itself proclaims that it is not at war, Washington and London are not violating neutrality by aiding Ukraine which is then likewise not at war — but is merely an unwilling host to an unwelcome Russian “SMO” on its territory.
This is yet another way in which Putin launching the war without a declaration of war hamstrings Russia.
First of all, it is dishonorable. Had Russia declared a war on February 24 it could have differentiated itself from the United States at least in this way. It could have been said that at least when Russia launches wars it is honest.
Second of all, since no war has been declared, Russian conscripts — who were already trained and already integrated in their units that relly on them — were procedurally unavailable for the war and had to be left behind. This very substantially limited available fighting strength of the Russian army and is a large part of the reason why it found itself stalled before even as much as capturing the whole of Donbass.
Finally, since no state of war exists legally, the West is even less deterred from interfering than it otherwise would have been. If even Russia itself insists that this is not a real war, but some sort of a vague “operation” then there really is no reason why US and Britain can’t be carrying out their “special military operations” in Ukraine as well.
According to previous reports, British SBS commandos traveled to Ukraine to train Ukrainian frogmen who led the landing on Snake Island after the Russian evacuation. (Ie, they were trained with that specific mission in mind.)
It’s possible that the British are likewise offering training to Ukrainian commandos who venture behind Russian lines. For example, it has been speculated that a string of explosions in Russian facilities in Crimea (beyond the range of HIMARS) has been the work of small drone teams operating from the Russian rear.
Another question would be are the British involved in mission planning, and are they in communication with their trainees during the mission.
The US Constitution says only the US Congress can declare war. The last time it did so was against Romania in 1942. https://en.wikipedia.org/wiki/Declaration_of_war_by_the_United_States#Formal