The 1925 Offside Reform and the Genesis of the WM Formation

On June 13, 1925, the International Football Association Board (IFAB) reduced the offside requirement from three defending players to two. Prior to this reform, defending teams had mastered the 'one-back game' — a highly negative strategy where one fullback stayed deep while the other stepped up to trap attackers, paralyzing match play with constant offside whistles and depressing goal-scoring. The SFA-proposed change immediately opened up attacking play. On the opening Saturday of the 1925/26 English Division One season, average goals per game rose to 3.7 compared to the 3.1 average of the previous season. Across the entire campaign, first-division goals surged by 43 percent, increasing from 1,192 to 1,703. Recognizing that traditional two-back defenses were now exposed, Arsenal manager Herbert Chapman withdrew his central midfielder into a deep central defensive role to create a third fullback, flanked by two half-backs, with two attacking midfielders supporting a five-man forward line. This structural adjustment layered the team into a 3-2-2-3 shape — resembling the letters 'W' and 'M' — which established the primary tactical template of European football for the next three decades.