The US sniper teams are a definite trope of TV and movies, but historically many armies have used solo snipers, without the spotter.
When I look for info, I either find gun info, sniper statistics or things about sniper training, but little info for the transition from sniper to sniper+spotter teams. Which much have been somewhat contentious as it cuts the potential number of snipers by half. Note that I don't question the idea in itself, anyone who's peered through a high power scope knows how much it "tunnel visions" you, but I am curious when the transition happened, what considerations went into it and who pushed for it.
Which other major militaries uses teams? By major militaries, I mean armies who made up their own doctrine rather than acting on the guidance of foreign advisers. Yes, yes, if you feel unhappy about multiple questions, consider that the primary one here is the US's transition to teams.
I am curious when the transition happened
During World War 1.
This is covered by the Wikipedia article
For the UK:
During World War I, Major Hesketh Hesketh-Prichard… developed many of the modern techniques in sniping, including the use of spotting scopes and working in pairs
Prichard, Hesketh; Vernon, Hesketh (2004). Sniping in France 1914-18: With Notes on the Scientific Training of Scouts, Observers, and Snipers (2004 ed.). Helion & Company Limited. ISBN 978-1-874622-47-5.
The development of US doctrine is described in History of the sniper
DURING WORLD WAR I, THE skill sets and standard operating procedures of our present-day snipers were developed and codified… Once he had a suitable modern weapon, the scout sniper emerged in a form identical to the present day. Now actually called a sniper,… he selects his hiding place carefully and uses camouflage to conceal himself and his spotter.
The UK entered WW1 in 1914, the US entered WW1 in 1917.
Which other major militaries uses teams?
UK armed forces also use a two-man spotter + sniper team. This may be normal practice in NATO countries.
It seems the Soviets started using two-man teams after WW2. From what I've read the Russians have the squad leader act as spotter.
Sniper functionality was a singular task in the 1750 - 1880 era of targeting enemy command till the invention of smokeless powder in ~1880. With black powder, the sniper's position was instantly apparent therefore a 2 team sniper would be at a double loss if eliminated. Once smokeless powder was available, the scope of what a team could do was slowly evolved. One must realize the actual targeting of enemy is just one of many tasks a multi-man team can accomplished. Recon of the enemy is the most valuable aspect of a team. They can study the enemy & determine the layout of the enemy positions, changing of units & leaders, visually identify the commanders therefore allowing their command to possibly recognize an enemy change of defense/offense. Lastly, takeout the key leadership @ proper time & place by direct/indirect fire or tach air. It is usually best to not allow the enemy to know you have sniper teams in play until situation dictates it. 1/9 Semper Fi