France, March 4 -- Tens of thousands of US troops are stationed across Europe on around 50 bases - a presence that dates back to the period after the Second World War, when Washington chose to keep forces on the continent to prevent another major conflict.

Many of those bases now carry out missions linked to NATO.

But in recent days, Washington has sought to use some of these facilities as part of its war in Iran, triggered by US-Israeli strikes that killed Supreme Leader Ayatollah Ali Khamenei and set off retaliatory Iranian attacks on US bases across the Middle East.

Host countries can refuse, because the bases remain under the full sovereignty of the states where they are located.

What was once a technical detail of military cooper...