The Performers
These are the soldiers described in "Who's For The Game." These are the men who have answered their countries call and joined up for the war. In Pope's ironically light-hearted conception of war, she describes these men as performers in a war game. Removing the grotesque and violent elements of war from the discussion, these soldiers become entertainers for the folks back home.
The Spectators
These are the men in "Who's For The Game" who have not gone to war. Pope describes them as non-participants, mere observers of the honorable game of war. Although they may not have joined up for various reasons, in Pope's thought experiment, they are all lumped together as passive agents watching their fellow men perform the truly difficult task of war.
The "War Girls"
These are the British women who have stepped up in the absence of the men who are all at war. They have thrown off their confinement into the private sphere in order to keep the country running. Working as ticket collectors, elevator operators, milk delivery persons, etc. they adapt to the more physically strenuous employments which previously were denied them. Pope praises these women for their courage and fortitude to embrace change and challenge themselves.
The British People
The people of Britain are the recurring subjects of Pope's poems. She is specifically writing about the Lost Generation, who participated in WWI. By accepting the dubious challenges of war and persisting in national unity, the British population proved their fortitude. In "No!" Pope praises the resignation of those who fought in battle, willingly accepting the possibility that they may be among those who don't return. Additionally, the entire population of Britain is lauded for their participation in the war, banding together to preserve their values as a unified whole to which everyone can contribute something.