Pawn on 4th v Pawn on 3rd:
Part of the Advanced Beginner's Chess Guide (Section 1) and the
Chess Strategies Guide (Section 2: Studying the Pawns)

Pawn on 4th v Pawn on 3rd
Point Count Chess: [+]

About This Article...

This article includes my notes, additional images and interactive chess positions from my study of Horowitz & Mott-Smith's book, Point Count Chess.

Source:
Point Count Chess,
Chapter 1. Pawn on Fourth v Pawn on Third (p25-26)

To help understand this concept better, Ken advised me to "Think of two armies approaching the front line in battle (White's front line being at the 4th Rank; Black's front line being at the 5th Rank, in Algebraic Notation terms.) ..."

"... If one army has advanced troops that controls territory beyond their front line, and can restrain the enemy with very few guards, it is an advantage. This is how it is when looking at the Pawn on the 4th v. 3rd situation."

In Diagram 1, below, we see that White's e-Pawn controls d5 - a square beyond its front line:

Pawn on the 4th v Pawn on the 3rd, Image 1, Advanced Beginners Chess Guide

Diagram 1: White's e-Pawn controls d5,
a square beyond it's front line.

In a 4th v. 3rd situation, the opposing Pawn must be on an adjacent file; it must be on the 3rd rank (not second), and the single square to the diagonal of the pawn on 4th, ahead of the pawn on 3rd, must be fully Controlled by the army, whose pawn is on the 4th Rank. If all three of these criteria are met, count yourself a point for 4th v. 3rd.

Diagram 1, shown again below, shows all three criteria being met by White:

Diagram 1: White's 4th v. 3rd Advantage

White's e-Pawn is on its 4th Rank; Black's d-Pawn is on its 3rd Rank; but, crucially, through the Pawn on the 4th, as it happens, White Controls the square immediately ahead of Black's 3rd Ranked Pawn.

Note that, if Black's c-Pawn attempted to take away the Control, of that crucial square in front of its own Pawn on the 3rd, by advancing to c6, that would only serve to substitute that one weakness, for another, by turning the d6-Pawn into a Backward Pawn.

Common sequences that create a 4th v. 3rd situation arise from the French Defence and Philidor Defence, respective:

French Defence:

Philidor Defence:

However, in the Scotch Game, while it's a close occurrence, there would be no plus point for White ...

Scotch Game