Vladimir Putin, the president of Russia, is not going to be deterred from invading Ukraine by ringing declarations from western summit meetings. So while it is important that the foreign ministers of the G7 nations should show a united and resolute defence of Ukrainian sovereignty at their two-day summit in Liverpool this weekend, it is not going to be decisive.
What will in the end put the Russian leader off trying to annex Ukraine, if it does, will be the huge cost and difficulty of maintaining the occupation of the country. Taking over the Crimea and parts of the Donbas region of eastern Ukraine, with their Russian-speaking populations, is one thing. Occupying the rest of Ukraine, a large, populous and proud nation, would on the other hand be a huge and expensive undertaking.
No one doubts that the Russian military would be capable of invading Ukraine. Russia still has armed forces out of proportion to its economic strength, as a legacy of the Cold War, and would probably prevail over Ukraine in a conventional war. But Mr Putin must know that controlling a population that would resist an occupation would be a different matter entirely.
