In an unprecedented plan to increase the level of international competition, the 54 UEFA member associations have unanimously agreed to launch a Nations League that will replace most friendlies starting in 2018. The competition will divide the 54 teams into four groups and will feature a promotion and relegation system with Euro qualification as the prize. It will exist within the current international match calendar.
UEFA's official website explains:
The UEFA Nations League and the EURO Qualifiers will be linked, with the new competition allowing an extra chance to qualify for UEFA EURO final tournaments. The competition and proposed amended qualifying formats for the European Qualifiers, starting with UEFA EURO 2020, came after a thorough consultation process with UEFA's member associations which began in 2011.
The exact format of the UEFA Nations League has not been finalised and will be the subject of further discussions between the UEFA member associations but the concept is for the 54 teams to be divided into four large groups according to coefficient rankings.
Teams compete to be promoted to a higher group or to become the UEFA Nations League champions and to qualify for EURO play-offs.

Prior to UEFA EURO 2020, each group will be divided into four pools of three or four teams so each team will play four to six matches between September and November 2018.

The final four competitions, involving the four pool group winners of group A, will start in 2019, whereas play-offs for the UEFA EURO will then take place in March 2020. National teams will thus either be competing to become UEFA Nations League champions or be fighting for promotion and to avoid relegation in their groups, as well as to qualify for the EURO play-offs.
The new competition is a response to "member associations, coaches, players and supporters [who] increasingly feel that friendly internationals are not providing adequate sporting competition." The more competitive structure with the reward of four teams qualifying for the European Championship through the Nations League will almost surely be more attractive to players and fans — two groups who have had a tendency to skip the meaningless friendlies that are more trouble than they're worth. So if those two groups are now more interested, the associations and coaches are sure to benefit.
If the format proves a success for UEFA, it seems probable that other confederations would follow their lead, thus finally ending the scourge of boring, time wasting friendlies once and for all.
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Brooks Peck is the editor of Dirty Tackle on Yahoo Sports. Have a tip? Email him or follow on Twitter! Follow @BrooksDT