Question about stunted movement/retreats

Hi there, I've only played the game like 1.4 times, and that was like a year ago so I'm a bit fuzzy on rules stuff. I just watched the learn to play in 22min video that was posted the other day and I had a quick question. While explaining movement, he mentions that you cannot move through a system with enemy ships in it to reach an activated system, you would stop in the unactived enemy system and begin space combat.

So here's a question, say I have 3 cruisers that want to move two spaces away to mecatol rex, but there is an enemy fleet in the space between. If I activate mecatol rex, and engage the enemy fleet in the system en route, can I then declare a withdrawal at the first round of space combat and withdraw into Mecatol Rex? Thus, travelling to Mecatol Rex, but also suffering a single round of space combat.