"AERA"（アエラ） is a weekly magazine released by Asahi Shimbun(朝日新聞）. I am looking forward to seeing a short message in its advertisement on a newspaper each week because it let me chuckle every time. It contains a kind of "word play".
This time, I try to explain it. We often use only one Kanji character to express a country's name or itself. For example, "米（べい）" means the United States of America. "仏（ふつ）" means France. "露（ろ）" means Russia and it also can be pronounced "つゆ". And "つゆ知らず in Japanese means that (a person has) "unconsciously" (done wrong or done something that he does not plan to do at first).
So, "日本の領土とは、露知らず？" has two means. The first is "it(or he) did something but it has been unconscious that it is Japanese territory". Another mean is "Russia has not known (or learned) that it is Japanese territory".
There has been a dispute on small islands near Hokkaido（北海道） between Japan and Russia. It is one of on-going issues that Japan has faced now. You can learn more about this problem
here.
