Can I offer a bit of context on the military voter for some context? This info is from a survey about the 2018 election. This is for all military members, not just those overseas. Last set of numbers I saw were around 170,000 overseas.
61% of the 1.3 million active duty military members were registered to vote in 2018. That was 12 percentage points less than the civilian population when adjusted for demographic differences.
26% of military members voted in 2018 compared to 52% of civilians with the same adjustments
49% of military members lacked interest in voting with 24% explicitly uninterested and 25% neither interested or uninterested.
When comparing 2014 election to 2018 elections
More military members requested an absentee ballot from 47% to 53%
More who requested a ballot received one from 36%to 42%
BUT fewer of those who did receive a ballot returned it from 82% to 78%
I also have a few more stats from 2018. These are for the non military overseas voter.
4.8 million U.S citizens overseas
2.9 million of them were eligible to vote.
135,507 ballots from overseas citizens were received
Source-
State of the Military Voter