pronouns - Using 'her' vs. 'its' to refer to a country

I am currently reading Liddell Hart's "History of the Second World War", and I'm wondering why he sometimes uses her/she when talking about Japan. In my understanding of English, it should be its or their (if you want to refer to the Japanese people).

For instance:

From 1931 onward the Japanese were aggressively engaged in expanding their footholds on the Asiatic mainland at the expense of the Chinese, ...

makes sense to me, but:

It is remarkable that she deferred striking for more than four month, while trying to negotiate a lifting of the oil embargo

or

Until early in 1941 Japan's plan in case of war against the United States was to use her main fleet in the southern Pacific in conjunction with an attack on the Philippine Islands, ...

does not.

Can somebody explain why Japan is female, and are there more countries for which her should be used?

Answer

Historically, "her" was commonly used as a pronoun for not only women, but also for both countries and ships (e.g. sailing vessels).

However, that usage has more or less fallen out of favor, and instead "its" has become the preferred pronoun. Nevertheless, you'll still see "she" or "her" used depending on the preferences of the author.

http://www.grammarphobia.com/blog/2007/01/is-a-country-a-she-or-an-it.html