New Delhi, March 25 -- Investors have grown accustomed to the idea that US President Donald Trump-induced shocks rarely last long, because, as the popular TACO acronym tells us, 'Trump Always Chickens Out.' But the American president's decision to join Israel in starting a war with Iran has opened a geopolitical and macroeconomic Pandora's box that may make a tidy walk-back impossible.

Under the surface, financial markets are starting to take note.

The 'TACO regime' in American stocks-under which every selloff was a buying opportunity-may be over. That thesis will now get a test after Trump postponed threatened strikes against Iranian energy infrastructure and power plants for five days, pending the outcome of what he said were talks wi...