Lavrentivs wrote:ταῦτα δὲ τὰ δέκα ἔτη ὁ πρῶτος πόλεμος ξυνεχῶς γενέμενος γέγραπται. (Th. 5.24.2)
What is ταῦτα?
Apologies for the late reply.
ταῦτα (accusative neuter plural of οὗτος) is here part of the phrase ταῦτα...τὰ δέκα ἔτη. This phrase is an accusative of time, denoting the duration for which something lasts (see Smyth's Greek Grammar
, sections 1582-3); it therefore means '[lasting for] these ten years'.
My own translation of Thucydides renders the passage you quoted as:
'The first war, which went on continuously for these ten years, has now been recorded.'
I hope this helps.