A chant to be heard around the playground after lunch... those who wanted to "join us" would link arms with the end person and join in the chant. We never actually got to play "Army" so I cannot tell you the rules or objectives. It was always time to go in by the time we had enough people. Even though we didn't know how many people you needed to play Army, as we had never played it.

We used to chant, "All join on for playing at army. NO GIRLS!"

God knows why, no girls ever wanted to play anyway.

Another variation, would start with a small group, usually lads (girls had no time for such frivolity), anms linked chanting "anybody in the way gets a big kick". For obvious reasons people would get out of the way and addthemselves to the line for fear of getting hoofed into next week. The upshot was of a hundred 8 year old nutters making more noise than an away terrace on a Saturday afternoon, frantically chasing stragglers round a playground, screaming. Bliss.

Our declaration of a game of war involved putting hands on our heads with the words "hands on heads whose playing war with the juniors". When this chant began just after daytime school began our teacher announced that "if we liked putting our hands on our heads so much we can spend the whole morning like it" as a result I am certain that he must have felt a surge of dirty adrenaline as it must have appeared to onlookers or anyone squinting that his whole class of 6 year olds had surrendered to him (in spite of the fact that we had a considerable numerical advantage)

An alarmingly similar phenomenon occurred in a Melbourne primary school in the early 1990s... precisely as above but with the chant changed to "Who wants to play? Fooo-ty?" (Chanted in time with marching of feet)

At our school the technique was...

Who.
Wants to play.
Arrrrrr-my.

You're welcome.

Who's playing.... "Cops And Robbers"?
Also "Batman & Robin", "Star Wars" (required one girl player (Leia), obviously).
Never played any of the games, although there was an abortive attempt at Star Wars, curtailed by rain.

Being a child of the 90s, the game that we recruited for in that manner was Power Rangers. We only needed about five, so the game did get started. Though actually by the time we'd sorted out who was which power ranger (me being the sole girl, I was invariably the pink one), it was time to go back inside. So still a pointless exercise.

our chant was "who wants to play war" or "who wants to play cowboys and indians". Depending on the game, obviously.
And unlike Army, War was easy. You're soldiers. You run around and shoot each other. "Army" rules and objectives - Jeez, are you some kind of girl Bridget. Oh.

A variation on this was 'who wants to play (random game)'. Everyone had to link arms and chant together.

A variation of this chant in earlier times (1960s) was "All in for Japs and English" which generally required a full morning playtime to gather in the requisite recruits with the battle taking place at lunchtime. The combatants on both sides of course all used the "huh-huh-huh-huh-huh" sub machine gun (as ably demonstrated by Peter Kay) and the winners (invariably English) were allowed to use the chant "We won the war, in 1964" throughout the afternoon playtime.

Anyone who attended Etherley Lane Junior Mixed and Infants School in the 1960s will be able to verify these facts.