New born and fiance leaving....

Guess • 🔹Married to my high school sweet heart🔹Mom of three amazing boys, Maverick born Jan 2017, Arius born Sept 2018, and Draxton born Aug 2021
Our son is 3 weeks old and yesterday my fiance got a call saying his unit got approved to go over seas for a training. They don't have a date yet and they don't know how long but said it could potentially be 3 months. They also have to go to a week long training prior to leaving and a 2 week long training shortly after returning so potentially 4 months he will be gone here very soon. I know the first year of babies lives are full of big milestones and I hate hate hate that he will miss so much. What can I do to make him feel like he isn't missing things? Also with him going to a diffrent country what's the best way to stay in contact phone wise?