Answer:
Pounced on, its basically like to give a surprise attack. For example, 'The cougar pounced onto the rabbit'.
Step-by-step explanation:
'Pounced on' is generally used for animals and such, but it can also be in these terms. Before war 'pounced on' the US on December 7, 1941. So, war was unexpected, and perhaps the US wasn't prepared for the war and made them have an economic crisis. I hope this is what you wanted! :)