A people who think of nothing but running away at a time like that — what a pathetic nation we are.
Literal
That-like time flee [only-しか] don't-think Japanese-people [topic-は] pathetic.
しか...ない used inside a verb-modifier (考えていない) gives '(people who) think nothing but.' This puts the limiting frame inside a relative clause modifying 日本国民. 情けない 'pathetic / shameful' here applies to the nation as a whole, an indictment rather than self-criticism. そのような is a slightly formal demonstrative — 'that kind of.'