Using no particle after verb

Hello, I'd look to know the difference between these two sentences:

日本に行きました。
日本に行ったのです。

Thanks!

The first one is simply a statement "I went to Japan."

The second would be used when it is given as an explanation/background, for example (sorry for the somewhat boring examples):
- Ureshisou desu ne. Nani ka ii koto ga arimashita ka? (You look happy. Anything good happen to you?)
- Nihon ni itta no desu. (It is that [That's because] I went to Japan!)

- Kirei na kimono wo kite imasu ne. (You are wearing a beautiful kimono.)
- Nihon ni itta no desu. (I went to Japan, so...)

- Tomu wo saikin mimasen ne. (We don't see Tom around recently.)
- Nihon ni itta no desu. (He went to Japan, that's why...)

Thank you!

素晴らしい答えを有り難う！

Note also that in colloquial speech, this の is abbreviated to ん.