I've always wondeered why the team squad is written with the backs, 15-9, then the forwards 1-8?

Just to confuse matters Rugby League numbering is the other way around. 1-7 are backs and 8-13 are forwards.

probably just to make sure you can see where backs end and forawards begin

l do not know the reason, Union, for some reason changed it in the 50's, the full back before then was number 1.

Maybe it was to be different to the league code, who continue to use the original numbering!

Good question!

They r numbered in the way that the team used to line up in the past; ie forwards at the front (1-8), backs behind (9-15).

The forwards r then numbered from front to back:
front row 1, 2, 3;
second row 4, 5;
back row 6, 7, 8.

The backs r numbered in the order they used to stand behind the forwards:
scrum half 9 (also called the inside half)
fly half 10 (also called the outside half)
centres 11,12
wings 13. 14
full back 15