Well, here is a guide where I'm going to tell you some "techniques" or game mechanics that can help you save some seconds of your RON speedrun!

𝗥𝗼𝗮𝗱𝘀: Roads help any kind of ground troops to move faster if they are moving trough one of this. They are made by clicking on a city, build road, and clicking another city on the map to make the road.

Here an example:

𝗕𝗼𝗿𝗱𝗲𝗿 𝗖𝗶𝘁𝗶𝗲𝘀 𝗮𝗻𝗱 𝗙𝗼𝗿𝘁𝘀: Sometimes you can find countries that have 2 cities that are by the border and are really close, in this scenarios you can build a fortress on the city of the country you control and move your troops there, after that, you can declare war on that country and make their troops move to that Border city to reconquer it, once they get there they will engage in combat with your troops that will have a defense boost cause of the fortress, making you lose less troops! and getting rid of the AI country troops.

Here an example:

𝗧𝗵𝗲 𝘀𝗵𝗼𝗿𝘁𝗲𝘀𝘁 𝗱𝗶𝘀𝘁𝗮𝗻𝗰𝗲 𝗶𝘀𝗻'𝘁 𝗮𝗹𝘄𝗮𝘆𝘀 𝘁𝗵𝗲 𝗳𝗮𝘀𝘁𝗲𝘀𝘁: As you may know, in RON there are biomes and terrains, that depending on which one your troops are, will get a certain debuff. You can check the terrain and the biomes on the map section. And sometimes... you can get around it! You shouldn't always take the closest distance cause it could have a heavier debuff than another route, maybe you could even choose to go by another country to get a better terrain, but quick! cause if you stay too long your troops on that country will get a debuff (supposing that that country isn't your ally).

Example:

And for last...

𝘁𝗿𝘆 𝗳𝗼𝗿 𝘆𝗼𝘂𝗿𝘀𝗲𝗹𝗳: Sometimes, you just need to try to come with unique ideas to get rid of the country's troops without losing too much troops, like for an example, you could make them go through debuff zones to weak them or make them enter the sea to destroy their troops with an boat. You will just find out by thinking and testing!

Example: