I just played in multiplayer for the third time. It was a rather large map, four players, I was in the lower left corner.
I wondered why the other players didn't attack me apart from a few tanks once and two VTOLs another time. I just assumed there were fighting among each other. I noticed the player in the upper left corner built massive amounts of defense structures around his base (mostly mini rocket towers and some kind of mortar pits). The player in the lower right seemed to build lots of hardpoints. I researched VTOLs and howitzers, attacked the player in the upper left corner taking out many defense structures before he built enough anti-air emplacements to kep my VTOLs away. I then built some howitzers on a hill outside the range of his mortars, and did the same to the player in the lower right corner. I added some defense structures to these hills and kept the VTOLs nearby, so when the players attacked the hills to take out the artilllery I was able to hold the hills. I then built sensor towers nearer to their bases, so that the howitzers could continue to attack them. When the bases were half destroyed both players left.
Now I wonder if they assumed that there was some implicit agreement not to attack before some point in time. Neither during game creatin nor during the game did anyone write a message indicating something like that though. Are such agreements common? If yes are they communicated somehow implicitly, in a way a newbie wouldn't notice?