Total War is a warmode (game mode) introduced as part of the Manhattan Project DLC. In this mode, technology updates from 1939 to 1942 and finally to 1945 at certain time intervals, depending on how much time has been set for the match. This can force a player to be rather cautious with his/her spending, as a large build-up of units from one era could leave you short on money in the next one, and leave you with an outdated and relatively obsolete force.
Total War mode is a sure way to show the skill of a player. It shows that a player can play a faction/factions regardless of time era. It shows that a player can manage his money, his troops and can adapt his tactics every time the time era changes.
In Total war, you don't have to research anything exept the units that need to be researched in 1939 but when the game cuts to 1942, they will be automaticly researched as well.