Russia Besieged (RB) is an AH Russian Campaign (RC) which has been subjected to "extreme makeover". It´s better looking, the rules are changed and there´s a lots of more chrome, but the base is still RC.
I played RC almost continuously for 2 years during high school and had also played a few games in recent years, so my nostalgia account is full regarding RC.
Sure, a lot has happened in game development and the RC is an outdated engine but RC's greatest assets (IMHO) are the nostalgia, charm and its fun.
So does RB add something? Appearance Both the map and the counters are larger than normal and of better quality, which is good. When I did my setup as the Russian, I noticed that my "spinal cord knowledge" of the defense doctrine in RC did not help. Small terrain changes on the map forces you to “think new”" which is good. Rules The obvious shortcomings of the RC, supply, soak off against the major cities etc has been fixed. In addition to these, the major changes are that the units now have two steps, the flight is more detailed, and you can attack "blitzkrieg style". Then, there is a variety of changes which I categorize under "chrome". Sometimes it feels like that the designer has made a change just to make a change, which creates a certain irritation, when all too often you have to look in the rulebook. I also agree with Lowell Drake review, that the weather chart is really quirky sometimes
There’s also some "design for effect" such as oil wells that provides much greater incentive for Germans to conduct "cases blau".
Game play You can compare the RB with a "tenderloin steak” at your local restaurant. There will be no revolutionary cooking or new flavors, but it's good.
Sometimes you want to be surprised, sometimes you just want a relaxing break after work, then RB works.
I cannot get pass the river rules. The rules that do not require attacker to soak off if behind river It makes build a defense line behind river a worse idea in lots of situations. This ruins the game completely, since RC/RB is less dramatic than other east front games and it is common to proceed the game to mid-/late-war, where river line defense and local counterattack are common. Otherwise it is a step up of the good old Russian Campaign.
I think the river rules work well. If you attack only part of a river line it may look good, but the ZOC still applies, so your units are stuck for the 2nd impulse and can't move. Rivers are very good places to form a defensive line.