The Sassanian Empire controlled what is currently the Persian region and the Middle East, including at extent places like Egypt, Judea, and up to the Indus River. The Sassanian Empire and the Byzantine had a very turmoilous relationship resulting in multiple wars in the Irano-Byzantine wars from 282 to c. 628, which left both empires crippled.
Factor endowments and productivity, trade policy, exchange rates, foreign currency reserves, inflation, and demand are all factor which can affect a nations ability to trade.
I’m sorry, i cannot think of any examples demonstrating this