It's the accursed Federation of Arden! They're invading Caloran!!
Oh wait, aggressor pop of 700. 700? Are you serious?? 700 folk with TL8 plan to oppress a couple million TL 5 folk?
700 souls - men and women, ages ranging from infancy to elderly, can't manage to send out more than a hundred folk under arms without compromising what little infrastructure they have - maybe double that defensively if the ones under arms can do other duties between drilling. You can threaten - atomics work nicely, assuming you're not in the Imperium. You can maintain influence wherever YOU happen to be. But you can not maintain your influence when you're not around - not without a lot of local help. You can be Vikings, but you can't be oppressors unless you can persuade some portion of the local pop to assist you in that.
Tech Level 5:
Efficient internal combustion engines burning volatile liquid fuels.
Effective radio.
Electric power grid.
Early aircraft.
Improvements in metallurgy.
Tech Level 4:
Steam power based on burning wood, coal or other fuels. Power plants are too bulky and inefficient for personal travel, might be serviceable for truck-like heavy ground transport where domestic animals are unavailable or can;t be used.
Very limited electricity based on primitive batteries and low power generators.
No practical radio, or radio limited to wireless telegraphy. In the former case, ships at sea can no longer call for help.
Lighting limited to kerosene lamps, candles, gas jets and the like.
No aircraft beyond balloons, blimps and possibly dirigibles.
Fundamentally, you're asking them to give up electricity and radio; most other TL 5 to 4 changes aren't going to have the same broad impact. Question is: why? That drop is going to seriously impair the industrial base, reducing your potential profits. Potential impacts on productivity in mining and farming as well - tractors go byebye, along with electric lighting, and powered equipment depends on steam.
Why downgrade the world's tech? Why, hmmm ... try this one on. Maybe there's a Chamax situation: the local fauna avoid humans and behave normally under ordinary circumstances but are riled up by radio sources or magnetic fields. The local humans have been struggling with an increasingly hostile environment ever since they started developing TL 5 tech - and they don't know why. You arrive in the midst of an impending disaster: the locals are stretched thin trying to keep the fauna at bay, food production is critically low as farms are overwhelmed, they're on the brink of famine and collapse, and they most decidedly don't have the strength to fight you off and keep the world's beasties at bay. So, they yield to you on condition that you find some way to save them from disaster.
Which you do. Rather than landing the armies to defend them as they expect (they don't have any way of knowing your numbers unless you tell them), you deduce the problem and order them to shut down their power production and radio communications. You go out and stage a few dramatic rescues with your superior firepower, helping those who obey, allowing those who do not to meet their deserved fate, using your ship to shuttle food and supplies from place to place to stabilize the situation, and gaining the gratitude of the people as the men from the stars who saved them from extinction. They agree to pay tribute.
In amongst the struggle and chaos, you plant bugs and learn the local "lay of the land", quietly eliminating those who might be problems and building up those who are your most effective supporters. By the time the people start questioning why they're still paying tribute, you have complete control of the local government, and the local leaders are afraid to speak against you even privately among themselves for fear of disappearing or finding themselves arrested by rivals.
Oh wait, aggressor pop of 700. 700? Are you serious?? 700 folk with TL8 plan to oppress a couple million TL 5 folk?
700 souls - men and women, ages ranging from infancy to elderly, can't manage to send out more than a hundred folk under arms without compromising what little infrastructure they have - maybe double that defensively if the ones under arms can do other duties between drilling. You can threaten - atomics work nicely, assuming you're not in the Imperium. You can maintain influence wherever YOU happen to be. But you can not maintain your influence when you're not around - not without a lot of local help. You can be Vikings, but you can't be oppressors unless you can persuade some portion of the local pop to assist you in that.
Tech Level 5:
Efficient internal combustion engines burning volatile liquid fuels.
Effective radio.
Electric power grid.
Early aircraft.
Improvements in metallurgy.
Tech Level 4:
Steam power based on burning wood, coal or other fuels. Power plants are too bulky and inefficient for personal travel, might be serviceable for truck-like heavy ground transport where domestic animals are unavailable or can;t be used.
Very limited electricity based on primitive batteries and low power generators.
No practical radio, or radio limited to wireless telegraphy. In the former case, ships at sea can no longer call for help.
Lighting limited to kerosene lamps, candles, gas jets and the like.
No aircraft beyond balloons, blimps and possibly dirigibles.
Fundamentally, you're asking them to give up electricity and radio; most other TL 5 to 4 changes aren't going to have the same broad impact. Question is: why? That drop is going to seriously impair the industrial base, reducing your potential profits. Potential impacts on productivity in mining and farming as well - tractors go byebye, along with electric lighting, and powered equipment depends on steam.
Why downgrade the world's tech? Why, hmmm ... try this one on. Maybe there's a Chamax situation: the local fauna avoid humans and behave normally under ordinary circumstances but are riled up by radio sources or magnetic fields. The local humans have been struggling with an increasingly hostile environment ever since they started developing TL 5 tech - and they don't know why. You arrive in the midst of an impending disaster: the locals are stretched thin trying to keep the fauna at bay, food production is critically low as farms are overwhelmed, they're on the brink of famine and collapse, and they most decidedly don't have the strength to fight you off and keep the world's beasties at bay. So, they yield to you on condition that you find some way to save them from disaster.
Which you do. Rather than landing the armies to defend them as they expect (they don't have any way of knowing your numbers unless you tell them), you deduce the problem and order them to shut down their power production and radio communications. You go out and stage a few dramatic rescues with your superior firepower, helping those who obey, allowing those who do not to meet their deserved fate, using your ship to shuttle food and supplies from place to place to stabilize the situation, and gaining the gratitude of the people as the men from the stars who saved them from extinction. They agree to pay tribute.
In amongst the struggle and chaos, you plant bugs and learn the local "lay of the land", quietly eliminating those who might be problems and building up those who are your most effective supporters. By the time the people start questioning why they're still paying tribute, you have complete control of the local government, and the local leaders are afraid to speak against you even privately among themselves for fear of disappearing or finding themselves arrested by rivals.