viðbragðinu
viðbragðinu is the dative singular form of the Icelandic word viðbragð. viðbragð itself translates to "reaction," "response," or "emergency measure." Therefore, viðbragðinu specifically refers to "the reaction," "the response," or "the emergency measure" in a context where the dative case is grammatically required.
The dative case in Icelandic is used to indicate the indirect object of a verb, the object
For example, one might say "ríkisstjórnin greip til hraðra viðbragðinu" which translates to "the government took