Well, this is what I read in his Narutopedia page:
"During the Nine-Tails' attack on Konoha, Itachi was left alone to take care of his infant brother Sasuke and told him that he would protect him no matter what."
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Itachi sensed something was wrong, Sasuke starts crying and itachi says he will protect him. He is wondering why his parents had to go out then and as from the chapter before this one you can see the nine tails isn't attacking yet.
Going to the manga will clear things up, since the narutopedia can be out of context.
I agree with you though, Kurenai should abandon her baby on the street and rush to war, even though she hasn't been training in over a year and will probably be killed within a day of war.