Why did battles take place along rivers

Because it was an easy source of water for their needs that required it and it was also and easy way to transport supplies to the battle sight if an army was in a foreign location. Hope this helps, if you need clarification let me know?

Assemblies do not have written codes of laws. laws are matters for magistrates and courts, not assemblies. codes of law are things such as civil law, criminal law, and constitutional law. what assemblies have are procedures regarding debating, voting and other business they might carry out.  also note that rome had three assemblies: the assembly of the soldiers, the assembly of the tribes, and the plebeian councils.