… evidenziate da Gideon Rachman sul Financial Times di ieri:

"America is back" proclaimed Joe Biden, a few weeks ago. But in Afghanistan, America is out. The US president has just announced the withdrawal of all American troops from the country. A 20-year war will end on the symbolic date of 9/11, 2021.
The watching world will wonder if a gap is emerging between White House rhetoric about re-engagement with the world, and a reality of continuing retreat. Biden insists that this is not the case. He argues that America has achieved its counter-terrorism aims in Afghanistan and now intends to "fight the battles for the next 20 years, not the last 20".
But perception matters. The danger is that the pullout from Afghanistan will be seen outside America as a Vietnamlike failure that could lead to the fall of Kabul to the Taliban, a replay of the fall of Saigon to North Vietnam in 1975.
ival powers, in particular Russia and China, could now be emboldened to test the Biden administration's resolve a little further. The obvious flashpoints are Ukraine and Taiwan. In recent weeks, the Kremlin has assembled more troops on its border with Ukraine than at any time since 2014 when Russia grabbed Crimea. Last week, China sent a record number of military jets into Taiwanese airspace. Both countries are combining military muscle-flexing with warlike rhetoric.
Biden himself has used confrontational language with Russia and China. He has called Vladimir Putin, Russia's president, a killer and his administration has branded China's actions in Xinjiang a genocide. The US also recently imposed sanctions on Russian and Chinese officials and has eased restrictions on American officials meeting their Taiwanese counterparts.
The strategic situation in Asia and Europe is similar in one key respect. The US has expressed strong support for both Taiwan and Ukraine, but neither country enjoys an explicit American security guarantee. The US relies on a policy of "strategic ambiguity" over Taiwan. The idea is that China should understand there is a strong chance that the US would fight to defend Taiwan, without a firm promise being made. In a similar way, the US has never spelt out what it would do if Russia launched a full-scale invasion of Ukraine.
Although Taiwan and Ukraine are separated by thousands of miles and involve different antagonists, the two stand-offs feel connected. Ivo Daalder, a former US ambassador to Nato, believes that: "Moscow and Beijing will look closely at how we react in one situation to set the stage for the other." Daalder argues that "we need greater strategic clarity on what we would do if Russia moved militarily against Ukraine, or China on Taiwan".
There are voices in the US calling for America to now make an explicit security guarantee to Taiwan, and for Nato to accelerate the process that would allow Ukraine to join its alliance. The hope is that these moves would deter Moscow and Beijing, and so reduce the risk of war starting by miscalculation. The argument against these policy changes is that China and Russia may interpret them as a threatening shift in the status quo — and feel compelled to respond. American allies in Asia and Europe may also feel that explicit security guarantees for Taiwan and Ukraine are too provocative. The joint statement issued by Biden and Yoshihide Suga, the Japanese prime minister, after a meeting last week, stressed the importance of peace in the Taiwan Strait, but remained vague about how Washington and Tokyo might respond if conflict broke out.
It would obviously be particularly difficult for the Biden administration to respond to simultaneous crises over Taiwan and Ukraine. Some western strategists are concerned that Moscow and Beijing may be co-ordinating their actions, to maximise the pressure on the Biden administration. They point to an increase in the frequency of high-level meetings between the Russian and Chinese governments. Beijing and Moscow also made statements, after a recent meeting between their foreign ministers, which signalled a deepening of their strategic relationship and a more open rejection of a western-led world order.
The internal situations in Russia and China may also be raising the dangers of conflict. Putin recently imprisoned Alexei Navalny, the most popular and dangerous opposition leader he has ever faced. Navalny is on hunger strike and may soon die, sparking further protests. The Kremlin knows that conflict over Ukraine boosted Putin's popularity back in 2014. Another small war may look like a tempting option.
As the Chinese Communist party prepares to celebrate the centenary of its foundation later this year, President Xi Jinping may be looking for a triumph over Taiwan. American officials believe that Xi and his advisers have convinced themselves that the US is in deep and terminal decline. They fear that the Chinese leadership may believe the US would ultimately back down rather than fight over Taiwan.
But even the most confident and nationalistic officials in Beijing and Moscow will still be conscious of the risks of head-on confrontation over Taiwan and Ukraine. The likelihood is that Russia and China will continue to use "grey zone" tactics that stop just short of all-out conflict. As America discovered in Afghanistan, it is much easier to start a war than to control its outcome.