Searching the internet I found some remnants of my very first Combat Campaigns which are similar to the strategic overlay concept. They go back a long way, one much further than I thought.
This one dates from 1998!
"DOUBLE DEUCE" STEEL PANTHERS 2 TOURNAMENT
This one is a little later from 2001.
DOUBLE DEUCE'S STEEL PANTHERS: WORLD AT WAR WEB SITE