Staraya Russa is captured by Turn 10, 18-23rd March, 1942 and never really changes, the problem for the Soviets defending it is that the town covers 3 hexes and it is therefore difficult to retain all three with such overwhelming Axis forces, esp. in the south and west.

Endgame: Demyansk

Once Demyansk was captured by the Soviets in Turn 9, 2-17th March, 1942, it was fairly easy to defend as the Axis forces were weaker in this area and there was only one hex to defend, which was made possible by both the Northwest Front (red symbols above) and the Southwestern Front (green symbols).

Demyansk under pressure earlier in the game

In this game, after losing Demyansk in Turn 9, 12-17th March, 1942, Axis forces counter-attack with strong air-support in Turn 10, 18-23rd March, 1942. The Soviets also attacked with air support in defence of Demyansk, which meant that the Axis ground support attack was diminished (on a 2/3 ratio, which meant that the Axis forces won one column-shift to the right on the CRT (Combat Results Table), but did not succeed in regaining Demyansk.

How differently things turned out in the endgame with many Axis forces defeated.

In summary, the Demyansk Shield was Staraya Russa, which consumed and distracted the heavier Axis forces.

Here are my notes on the Campaign Game that I played in July 2020, showing, in particular the total of the Victory Points (VP's) at the end of the game:

German Reinforcement Chart
First line is asking for a Ju88 B-1, but there is no such piece according to Boardgamegeek. Ju88 1-B used instead as only one left after set-up chart.

2nd GRC Exit:
The table on the player-aid card suggests that the exit should take place at hexes 3634 or 4628, in fact the exit hexes are 4027 & 4031 for game turns 5 to 8, according to the map and the Rules of Play booklet (5.34a), page 5.

Victory Points (Game play July 2020)

2 GRC non-exit Turn 6 -6
2 GRC non-exit Turn 7 -6
Demyansk surrounded Turn 8 +3
Demyansk held Turn 9 +4
Axis initiative Turn 10 +2
Demyansk held Turn 10 +4
Staraya Russa held Turn 10 +4
Demyansk held Turn 11 +4
Staraya Russa held Turn 11 +4
Demyansk held Turn 12 +4
Demyansk held Turn 13 +4
Demyansk held Turn 14 +4
Demyansk held Turn 15 +4
Soviet Initiative Turn 16 -5
Demyansk held Turn 16 +4
Staraya Russa held Turn 17 +4
Demyansk held Turn 17 +4
Villages held Turn 18 +28
Soviet rocket & artillery units lost -8
Axis artillery or exploitation capable units lost +6

Final Total +62

+ 55 required for Soviet victory = marginal strategic victory for Soviets