Sebastian Vettel claimed a dominant victory in the Belgian Grand Prix as a dramatic first-corner crash provided the major talking point on Formula 1's return from its summer break.
Vettel drafted title rival and poleman Lewis Hamilton on the Kemmel Straight on the opening lap, drafting past the Mercedes as the Racing Point Force Indias of Esteban Ocon and Sergio Perez almost made it four-abreast heading towards Les Combes.
Ocon backed out having pulled almost level with Vettel, which allowed Vettel to hold the lead from Hamilton as Perez swept around the outside of Ocon into third.
That happened just before the race was neutralised following a massive first-corner crash in which Alonso was pitched airborne over Charles Leclerc.
Nico Hulkenberg locked both front wheels on his Renault and slammed into the rear of Alonso, who was launched into the back of - and then over - Leclerc, hitting the Sauber's halo device on the way down.
All three cars were eliminated on the spot, and the drivers emerged under their own steam.
Daniel Ricciardo's rear wing was broken by the flying Alonso, which contributed to the Red Bull running wide through La Source and inflicting a right-rear puncture on Kimi Raikkonen's Ferrari.
Ricciardo and Raikkonen pitted for repairs before rejoining, although they did not complete the race - Raikkonen stopped a few laps later while Ricciardo, who fell two laps down as Red Bull worked on his car then returned to the garage with 13 laps to go.
The safety car was out for four laps following the crash, with Hamilton half-attacking Vettel into the final chicane at the restart but falling into line with a small lock-up.
Vettel quickly built a three-second lead that he maintained until Mercedes brought Hamilton in on lap 21, with Vettel following suit one lap later at exactly the halfway mark.
Hamilton's rapid out-lap threatened to put him in position to attack Vettel but he caught the Red Bull of Max Verstappen at the end of the lap, which meant Vettel emerged out of DRS zone.
The Ferrari quickly re-established its healthy advantage, as Hamilton drifted back and eventually finished 11s behind, meaning Vettel cut the championship gap to 17 points.
Verstappen scored a lonely third place having got ahead of the Force Indias early on, drafting Ocon on the run to Les Combes three laps after the restart and pulling the same move on Perez a few laps later.
Verstappen ended up half a minute behind the winner and roughly the same amount clear of Valtteri Bottas, who claimed fourth in the closing stages.
The Mercedes driver started at the back after exceeding his engine limit for the season by taking the manufacturer's upgraded engine, but climbed steadily up the order and passed Perez with just a few laps to go.
That demoted the 'new' Force India team to fifth and sixth on its debut, as its 18-point haul immediately put the entry ahead of Williams in the constructors' championship and just one point behind Sauber, which only stays ahead because of Marcus Ericsson's 10th-place finish.
The new Force India also matched the best points haul for a team on its F1 'debut', equalling the 18 points earned by Mercedes (in 2010) and Brawn (in 2009, under the old 10-8-6-4-3-2-1 points structure).
Haas duo Romain Grosjean and Kevin Magnussen enjoyed a quietly effective grand prix to finish seventh and eighth, which moved the team to just six points behind Renault in the fight for fourth in the constructors' championship.
Carlos Sainz Jr's 11th meant Renault failed to score for only the second time this year.
Newly-confirmed 2019 Red Bull driver Pierre Gasly bagged two points for Toro Rosso and Honda in ninth place, with Ericsson completing the top 10.
|3||Max Verstappen||Red Bull/Renault||44||31.372s|
|5||Sergio Perez||Force India/Mercedes||44||1m11.023s|
|6||Esteban Ocon||Force India/Mercedes||44||1m19.520s|
|9||Pierre Gasly||Toro Rosso/Honda||44||1m45.892s|
|10||Marcus Ericsson||Sauber/Ferrari||43||1 Lap|
|11||Carlos Sainz Jr.||Renault||43||1 Lap|
|12||Sergey Sirotkin||Williams/Mercedes||43||1 Lap|
|13||Lance Stroll||Williams/Mercedes||43||1 Lap|
|14||Brendon Hartley||Toro Rosso/Honda||43||1 Lap|
|15||Stoffel Vandoorne||McLaren/Renault||43||1 Lap|
|-||Daniel Ricciardo||Red Bull/Renault||28||Accident|
|12||Carlos Sainz Jr.||30|