The U.S. decision to expel 60 Russian diplomats came after the U.K. told the Trump administration that was roughly the total number that European countries were expected to throw out, a European diplomat tells Axios.

Why it matters: The U.S. is expelling far more Russians than any other country, including the U.K., where double agent Sergei Skripal and his daughter were poisoned with a nerve agent March 4. President Trump's move is particularly surprising given the many times he has been criticized for not taking a stronger stand on Russian aggression.

By the numbers: In response to the Skripal poisoning, the U.K. expelled 23 Russian diplomats on March 14. Every country that took action Monday other than the U.S. and Ukraine, which expelled 13 Russians, threw out between 1 and 4.

144 Russian diplomats in total are to be expelled from Western countries at last count— 151 when you include the 7 expelled by NATO. That total is higher than for any single incident in Soviet or post-Soviet history.

are to be expelled from Western countries at last count— 151 when you include the 7 expelled by NATO. That total is higher than for any single incident in Soviet or post-Soviet history. 55 will be expelled from European countries other than the U.K. — a number close to the U.K. estimate of 60, though just 35 of those come from within the E.U.

other than the U.K. — a number close to the U.K. estimate of 60, though just 35 of those come from within the E.U. 26 countries in total are expelling Russians.

How it happened: Over the last week or so, the U.K. held frequent conversations with western allies to brief them on the evidence against Russia and to promote common action, said the diplomat, who is familiar with the discussions but asked not to be identified.