The effect of 'Icarus Attack' activates in the Damage Step; this timing allows chaining to the activation of your opponent's card effects that would prevent your monster's destruction by battle, such as "Solemn Judgment", but you cannot chain 'Icarus Attack' to the activation of your opponent's 'Infinite Impermanence', as Impermanence's effect activates during the Battle Phase, before the start of the Battle Step.