I would like to start with some very illustrative games to demonstrate the dominating mood in the chess world in the pre-Steinitz era.
1.e4
e5
2.f4
Of course the most popular opening of the mid-19th century. Conventional wisdom at the time assumed that White had an obligation to fight for the initiative at any price. That is why material sacrifice at an early stage of the game was simply a show of good taste, and to decline the opponent's kind material offer was not considered an honourable option.
2...exf4
3.Nf3
g5
4.h4
g4
5.Ne5
One of the key-positions of underdeveloped chess theory.
5...Nf6
6.Bc4?
[6.d4
was later proved to be a much better move.]
6...d5
7.exd5
Bd6
8.d4
Nh5
9.Bb5+?!
c6!
Anderssen in action! It's time to change colours and play white!
10.dxc6
bxc6
11.Nxc6
Nxc6
12.Bxc6+
Kf8!
13.Bxa8
Ng3
14.Rh2
Obviously the unknown club player who was playing white it wasn't clear whether Black had sufficient compensation for the sacrificed rook. And what do you think now about the options, e.g. [14.Kf2
Nxh1+
15.Qxh1
g3+
16.Ke1
Qe7+
17.Kd1
Bg4+
18.Bf3
Bxf3+
19.gxf3
Rg8
20.Qg2
Qxh4
21.Ke2
Qh2
22.Kf1
h5
and marching the h-pawn decides the game.]
14...Bf5
15.Bd5
Kg7
16.Nc3
Re8+
17.Kf2
Qb6
Any modern player would be jealous about Andersen's confidence in playing with a rook down. Meanwhile Be5 is a decisive threat.
18.Na4
Qa6
19.Nc3
[19.c4
Qxa4!!
20.b3
(20.Qxa4
allows mate in three: 20...Re2+
21.Kg1
Re1+
22.Kf2
Rf1#
) 20...Qd7
and White is defenceless.]
19...Be5!!
20.a4?
A primitive defence, preparing Nb5, but allowing Black's final beautiful combination. [20.dxe5?
Qb6+
21.Ke1
Qg1+
22.Kd2
Qe3#
is easy, but even the computer defence; 20.Kg1
doesn't save White: 20...Qb6
now Anderssen's idea doesn't work: (20...Qf1+
21.Qxf1
Bxd4+
22.Be3!
) 21.Rh1
Bxd4+
22.Kh2
Qf6!
is crushing]
20...Qf1+!!
21.Qxf1
Bxd4+
22.Be3
Rxe3
and mate in one is inevitable. Check it yourself. Despite the obvious inequality in the players' strength this game gives a clear idea of the chess fashions of Anderssen's time.
23.Kg1
Re1#
0-1