The main stars of the favorite teams arrived in the playing hall and played their first games at the Olympiad. World women champion Hou Yifan became an exception, her friends in Chinese team bested the opponents without her.
The results of the starts differed. Sometimes there were mistakes.

Al-Modiahki (2542) - Ivanchuk (2769)
Qatar - Ukraine

White lost the game of maneuvers, but complicated it in time:
40.f5! exf5 41.Qh4
Without the protection of its people Black king is in danger.
41...Qb5 [41...b5 would be followed by cunning 42.Qh6!] 42.Rb2
Playing for a win. In the line 42.Rh2 Qb1 (42...h5 43.gxh6 Kh7 44.Qd8!) 43.Qxh7+ Kf8 44.e6! Qxc1+ 45.Kg2 Qd2+ 46.Kh3 Nf4+ Black gives a perpetual check.
42...Qd7 43.Rh2 h5 44.gxh6 Kh7 45.Rf2 b5 46.g4 fxg4
More reliable is 46...Ra6 47.gxf5 gxf5 48.Qh3 Rg6+ 49.Kf1 Rg4 50.Qf3 f4 51.Rg2 Rg6=.
47.Kh2
The way to a draw is in 47.e6 Qxe6 48.Qd8 f5 49.Qf8 Qf6 50.Qc5 Qe6 51.Qf8 Qf6=.
47...Ra6 48.Kg3 Nxc3 49.Qxg4 Qd5?!
To no purpose. d5 square should have been left for the knight by 49...Qb7 or even 49...f5!? 50.exf6 Qf7.
50.Kh2!
Important prophylactics. 50.Qf3? did not work due to 50...Ne4+ 51.Kh2 f5!
50...Ne4 [50...f5 51.Rxf5!] 51.Rf4 f5 52.exf6?!
Wonderful complications 52.Rxf5! g5! 53.Bxg5 Rg6 54.Qf4 c3 55.Rf7+ Kh8 56.Rf8+ Kh7 57.Qf7+ Qxf7 58.Rxf7+ Kg8 59.h7+ Kxf7 60.h8Q Nxg5 ended in not less sharp, but equal endgame.
52...Nxf6 53.Qc8

The final of the game impressed the whole world. Ivanchuk should have looked for the counter threats without losing a minute. For example, by 53...Re6 or 53...Qh5+. In all the variations Black at least held even.
But 53...Rc6?? followed, literally pushing the White queen where it aimed to go.
Black immediately resigned because after 54.Qf8 his position is hopeless.

Papaioannou. I. (2606) - Kramnik, V. (2797)
Greece - Russia

White got a strong initiative for the pawn, Black has difficulties to finish the development. Vladimir decided to strike the Gordian knot with the sword:
16...Qxb6! 17.Nxc6 Qxb2 18.Rc2 bxc6 19.Rxb2 Rxb2
Compensation for the queen is enough for equalization.
20.Bd4 Rb5 21.e4 e5 22.Ba7
Strange placement of the bishop. Better was 22.Bc3.
22...Bb7
Interesting was 22...c5 23.Bf1 Rb7 24.Qxa6 Nxe4, but it is not in Kramnik's style to go for such an unusual continuation.
23.Bf1 Rb2 24.Qa5 Rb3
Declining playing for a win. In the different situation, in the individual tournament, ex-world champion could play 24...Nxe4!? 25.Rxd7 (White is worse after 25.f3 Nf6 26.Qc3 Rb5 27.Bxb5 axb5) 25...c5! 26.Rxb7 Rxb7 27.Qxa6 Rb1 with a sharp struggle.
25.Bc5 Bxc5 26.Qxc5 d5 27.Qc2 Rb6 [of course not 27...Rxa3? 28.Qb2]

28.Qc5
It seems, some winning chances were left for White after 28.Rb1 Rxb1 29.Qxb1 Ba8 30.exd5 cxd5 31.Bxa6 d4 32.a4, but it was not easy at all to estimate the further complications at the board.
28...Rb3 29.Qc2 Rb6 30.Qc5 1/2

Topalov, V. (2752) - Amonatov, F. (2610)
Bulgaria – Tajikistan

On the first glance, easily won endgame for White, it is in fact full of drawing resources.
34.Bc3
The main idea of Black can be seen in the variation 34.Kb5 Kd5 35.Bxa5 (quite more accurate is 35.h4!, on which even more accurate 35...f5! follows with the study-like escapes in the cunning lines) 35...Bxa5 36.Kxa5 Kc5! – the pawn-eater is in a cage on the edge of the board and there are not enough tempos to help him: 37.h4 (37.f4 g5!) 37...g5 38.h5 h6 39.b4+ Kc6 40.b5+ Kc5 41.b6 Kc4 42.f4 gxf4 43.g5 – in case of passed pawns race, White is saved for he converts his pawn on g8 into queen with check. And after 43...fxg5 there is a stalemate.
34...Bd8 35.f4?
Inaccuracy that costs half a point. Probably, winning was 35.Kb5 Kd5 36.h4!, for example, 36...g5 (or 36...g6 37.Bxa5 Bxa5 38.Kxa5 Kc5 39.g5 f5 40.f4 with the decisive zugzwang) 37.h5 h6 (as bad is 37...Kd6 38.Bxa5 Bxa5 39.Kxa5 Kc5 40.h6+-) 38.Bb2 Kd6 39.Ba3+ Ke6 40.Bc5 – and either h6, or a5 is a fruit to harvest.
35...g6 36.Kb5 f5! 37.gxf5+ [no better is 37.g5 Bc7!] 37...Kxf5 38.Bxa5 Bxa5!
Accurate calculation.
39.Kxa5 Kxf4 40.Kb6 g5 41.Kxb7 h5 42.a5 g4 43.hxg4 h4! 44.a6 h3 45.a7 h2 46.a8Q h1Q+ 47.Kb8 Qh8+ 48.Ka7 Qa1+ 49.Kb7 Qh1+
Perpetual check! 1/2

But most often the skill of the best players of the world prevailed. And the luck that comes with it.

Aronian, l. (2816) - Rahman, Z.(2516)
Armenia - Bangladesh

34...Qc6??
A blunder. Elementary 34...g6 kept the equality.
35.Qxf7+! Mate is inevitable, Black resigned.

Nakamura, H. (2778) - Malisauskas, H. (2451)
USA - Lithuania

The game is equal. But Vidmantas got too tired and it swept away...
92.Kc1!
Interesting idea.
92...e3?!
Already inaccuracy. As it occurred, the Black pawn is moving to its death.
Black should have checked with 92...Qg1+, or simply activate the queen - 92...Qa5.
93.Kd1!
The king embraces the Black passed pawn.
93...Qa5 94.Ke2 Qc3?
Yet to the draw leaded 94...Qb4! 95.Qf3+ (or 95.Qf7+ Ke5 96.Qd7 Qc5) 95...Ke5 96.Qxe3+ Kd5 and so on.
95.Qf7+ Ke4 96.Qe6+ Kf4 97.Qd6+ Qe5 [97...Ke4? 98.Qc6+!] 98.Qb4+ Kf5 99.b6
Black is forced to give a pawn and go into formally drawish endgame which is absolutely lost on practice.
99...Qh2+ 100.Kxe3

100...Qg1+
The question mark is not in place here, because it is not possible for anybody to play according to the nuances of Nalimov base on the 6th hour of the game.
Only 100...Ke6! leaded to salvation, for instance, 101.b7 Qg3+ 102.Kd4 Qf4+ 103.Kc5 Qc7+! 104.Kd4 Qf4+ 105.Kc3 Qc1+ 106.Kb3 Qd1+!, and White cannot avoid perpetual check and keep b7 pawn - 107.Kb2 Qe2+ 108.Ka3 Qa6+ 109.Kb3 Qd3+ 110.Ka2 Qe2+ and so on.
101.Kd3 Now everything is over. 101...Qf1+ 102.Kd4 Qg1+ 103.Kc4 Ke6 104.b7 Qf1+ 105.Kc5 Qf8+ 106.Kb5 Qf1+ 107.Qc4+ 1–0

Wang,Hao (2726) - Caruana, F. (2773)
China - Italy

Black has some compensation for a pawn, but for the salvation he needed study-like accuracy.
33...Nc2?
Not there. White pawns should have been attacked with the knight from с6, and the prophylactic move 33...Bd7! contributed to it. And in case of d4-d5 Black had time to centralize the king.
34.d5 Bd7 [or 34...Be8 35.c6] 35.c6! bxc6
In case 35...Bc8 36.Ne4+ Ke5 the easiest is 37.d6 bxc6 38.Bxa6!.
36.Bxa6 Nb4 37.Bb7
There is no way to take care of the pawn on the edge, Black king has no tempo for that.
37...cxd5 38.a6 Nxa6
Or 38...Bc6 39.Bxc6 Nxc6 40.Nb5!.
39.Bxa6 and White went to win with an extra piece.

I would like to pay attention to a few more spectacular fragments of the second round games.

Naiditsch, A. (2712) - Mchedlishvili, M. (2659)
Germany - Georgia

Black is deliberately asking to start a fire on him, and ... it started.
20.g4! hxg4 21.hxg4 Ng7 22.f5!
White enrolled his bishop into play and limited the bishop of the opponent.
22...gxf5 23.gxf5 Re8 24.Rf1!
An important nuance.
24...Qe7 25.Bg5 Qe5 26.Bf4 Qe7 27.Qg2! Nfh5 28.Bd2!
For quite a time Arkady is commanding the attack skillfully.
28...Qh4 29.f6?!
A mistake. 29.Rf3! would finish it, with the unstoppable threat Rf3-h3.
29...Bh3 30.Qf2 Ng3?
Prolonged the way or even completely prevented the collapse 30...Qg3+! 31.Qxg3 Nxg3 32.fxg7 Nxf1 – and it's not a fact that the endgame is won for White.
31.Re1 Rxe1+ 32.Qxe1 Bf5 33.Bxf5 N7xf5 34.Qe8+ Kh7 35.Qxf7+ Kh8 36.Qe8+ f6-pawn is moving to the aim. Black resigned.

Jakovenko, D. (2722) - GM_Kotronias, V. (2589)
Russia - Greece

It seems that Black has a good compensation for an exchange, and White's king is not comfortable. The decision of Dmitry is very nice.
19.Ke2! Nc2 20.Rac1 Nd4+ 21.Kd3!
The king is most comfortable exactly in the center. He is not threatened with anything.
21...Qf7 22.h5 Ne7 23.h6 [even better is immediate 23.Nb5] 23...Be5 24.Nb5 Nxb5
Or 24...c5 25.Nxd4 Bxd4 26.Nf3 Be3 27.Qd7! Bxc1 28.Rxc1 with the win for White.
25.cxb5 Nxd5
A sacrifice of desperation.
26.exd5 Qxd5+ 27.Kc2
Survived once check and going back to his people. Extra rook is deciding the game.
27...Qxa2 28.Kd1 Qf7 29.Qf3 d5 30.Re1 Bxb2 31.Rc2 Bd4 32.Qa3! Bb6 33.Re7 Qf8 34.Rcxc7! , and because of 34...Bxc7 35.Qc3+ Kg8 36.Rg7+ Black resigned.

Short, N. (2698) - GM_Fier, A. (2582)
England - Brazil

Nigel chooses the most beautiful from all decisions.
30.Ng5! Queen sac! 30...Nh6?
He should have ended the game esthetically: 30...Qxe2! 31.Nf7+ Kc8 32.Rc7#, but, alas, in our material time the coauthoring is not very valued.
31.Qxe5 Bxe5 32.Re1 Bf4 33.Nxe6+ Kc8 34.Re4 Be3+ 35.Kf1 Rb6 36.Nxc5
And White had to win the game in a dry material manner.

Tkachiev, V. (2644) - Pacheco, M. (2383)
France - Peru

Black was playing too passively in the opening. The punishment was severe.
18.d5! exd5
Leaded to the defeat18...Bxb5 19.dxe6! fxe6 20.e5! and White queen is aiming for g6.
19.Nxc7! Qxc7 20.cxd5
White not only wins the piece back, but also keeps the great initiative on the White squares.
20...Nc5
A little more stubborn is 20...Rac8 21.dxc6 Ne5 22.f4 Qxc6!.
21.dxc6 Rad8
The same answer from White followed after 21...Re7.
22.e5! A new surprise. 22...dxe5 23.Bd5 Rxd5
The problem of Black is not only in the weakness of f7 - 23...Rf8? 24.Qxg6.
24.Rxd5 Qxc6 25.Qc4
It is the matter of technique to win with an extra exchange. Vlad finishes it off in the same energetic manner.
25...Qc7 26.Red1 Qe7 27.Qb5 e4 28.Qxe8+! Qxe8 29.Rd8 Kf8 30.Rxe8+ Kxe8 31.Rd6 Bxb2 32.Rxb6 Nd3 33.Nxe4 a4 34.Nc5! 1–0

The results of the teams in the men's section did not surprise. Strong squads convincingly bested the opponents.
Women's tournament went on without unexpected flows, too. Those who were supposed to win according to their ranking, indeed won.
Apparently, we have to wait for the clashing matches of the favorites, only then the real intrigue will emerge.