I just recently noticed a soldier posted at River Valley. Has he always been there, or is he a recent addition?

20 years ago maybe. Since Hard Truck 2 (original US release, very first game version) and Hard Truck 2 King of the Roads 1.3 (third EU release which ones also differ, in russia it sold as two differ edition with non-compatible patches) is almost two differ games, many content can be new to you if you play original release.

[url=http://www.rnr-wiki.ru/index.php/%D0%98%D1%81%D1%82%D0%BE%D1%80%D0%B8%D1%8F_%D0%B2%D0%B5%D1%80%D1%81%D0%B8%D0%B9_(%D0%94%D0%B0%D0%BB%D1%8C%D0%BD%D0%BE%D0%B1%D0%BE%D0%B9%D1%89%D0%B8%D0%BA%D0%B8_2]http://www.rnr-wiki.ru/index.php/%D0%98%D1%81%D1%82%D0%BE%D1%80%D0%B8%D1%8F_%D0%B2%D0%B5%D1%80%D1%81%D0%B8%D0%B9_(%D0%94%D0%B0%D0%BB%D1%8C%D0%BD%D0%BE%D0%B1%D0%BE%D0%B9%D1%89%D0%B8%D0%BA%D0%B8_2[/url])

as almost always (every game) newer versions and patches sometimes los some features content or make it worse. Some old GFX effects benn better in HT2.

As for soldier posted, i not remember that. Maybe language version differences too, although they shouldt be so differ for 1.3 EU based localisation, i guess.