How they qualified By limping over the line. Colombia did not win any of their last four qualifiers. They also failed to win any of the six matches against Brazil, Argentina and Uruguay. Indeed, they were only actually victorious in seven of 18 group games. Still, at least a 3-2 friendly win over France offers some encouragement.
Manager Jose Pekerman. In his third World Cup, he has reached the quarter-finals in the first two, with his native Argentina in 2006 and Colombia in 2014. He was criticised for leaving Lionel Messi on the bench 12 years ago, but masterminded his adopted country's best ever World Cup campaign four years ago.
Player to watch Radamel Falcao. Colombia's record scorer missed the 2014 tournament with a serious knee injury that seemed to end his days as a major force, but he has returned to devastating form with 54 goals in his last two seasons for Monaco and has displaced Carlos Bacca to become his country's main striker again.
Talking point Can James Rodriguez repeat his form of 2014? The No 10 was not merely the top scorer in the last World Cup; he arguably scored the best goal, too, with a spectacular volley against Uruguay. Yet it proved the prelude to a difficult three years at club level, prompting a £63 million move to Real Madrid, where he ended up an expensive bit-part player. But he has been revived both on loan at Bayern Munich and in his country's colours. None made a bigger contribution in qualification, with Rodriguez scoring six and assisting four of Colombia's 21 goals.
Prediction An experienced manager Pekerman has stuck with some of his older players, and the precocious Davinson Sanchez is not certain to start, but it does prompt questions if they are too old, particularly in a central-midfield combination of Abel Aguilar and Carlos Sanchez, while goalkeeper David Ospina's mistakes in qualifying offer another worry. But any team that could have Bacca and Luis Muriel on the bench has plenty of firepower. In a group as potentially tight as this one, that could prove crucial but Colombia will do well to repeat their feats of 2014.
Read more on World Cup 2018:
World Cup 2018: Guides, predictions, galleries and where to watch in UAE
How they qualified Quickly; only Brazil and Iran qualified sooner. Yet Japan finished only one point ahead of Australia, who went into the play-offs and poor form in friendlies helped account for the April firing of manager Vahid Halihodzic, who had selected 68 players in three years. It is scarcely ideal preparation.
Manager Akira Nishino. An Asian Champions League winner as a manager, but the technical director of the Japanese FA until he plunged into the main job on a short-term deal. Halihodzic reportedly lost the confidence of the players so it is imperative former Japan international Noshino makes a better impression.
Player to watch Keisuke Honda. The first Japanese player to score in two World Cups could become the first to find the net in three. One of his country's most successful footballing exports, Honda turns 32 before the tournament begins and may not play the full 90 minutes, but he remains a fine finisher.
Talking point How many of the old guard will Nishino pick? While it would be rash to make radical changes with so little time to implement them, Halihodzic omitted some of Japan's more established players. It remains to be seen if his successor restores Honda, Shinji Kagawa, who had not been called up since October, and Shinji Okazaki to the starting XI. It makes sense to plump for footballers who have some experience of playing alongside each other, but it could come at a cost to some of the newer breed, like Genki Haraguchi, who scored in four consecutive qualifiers, and may seem unfair to them.
Prediction Japan are in their sixth consecutive World Cup. They have only reached the last 16 in two and to qualify for a third time would represent a successful tournament. The opening game against Colombia looks particularly tough: Japan have played South/Central American opponents in four World Cups and lost all four, including a 4-1 defeat to Colombia four years ago. Two of their four previous wins have come against African teams, making their second game, against Senegal, particularly pivotal. But a side ranked 60th in the world have much to do to bely their status as outsiders in the pool.
Read more on World Cup 2018:
In pictures: All 12 Russia 2018 World Cup stadiums
How they qualified Seemingly impressively, finishing five points ahead of Denmark in Group E. Yet they lost 4-0 to the Danes and needed late goals to clinch wins against Armenia and Montenegro. The encouraging element is that they scored 28 times in 10 games; the worrying part is that they conceded 14.
Manager Adam Nawalka. A former Poland international who played in the 1978 World Cup. He took over in 2013 when Poland were ranked a lowly 69th in the world. Now they are in the top 10 and reached the quarter-finals of Euro 2016 under the 60 year old, a former Trabant car salesman.
Player to watch Robert Lewandowski. Poland's record scorer set a European record by scoring 16 times in a World Cup qualifying group. He also reached 40 goals in a third consecutive season for Bayern Munich, but their Champions League exit left questions about his big-game record and he only scored once in Euro 2016.
Talking point Has this come at the wrong time for Poland? A group of their key players, including Kamil Glik, Michal Pazdan, Lukasz Piszczek and Jakub Blaszczykowski, are in their thirties. Blaszczykowski and Arkadiusz Milik have had injury-ravaged seasons at club level, while Grzegorz Krychowiak failed to produce his best form as West Bromwich Albion were relegated. The sense is that more of their squad were nearer their peak at Euro 2016 and those who are better players now, such as Napoli midfielder Piotr Zielinski, are in the minority. Is it a tournament too far for some of his teammates?
Prediction Poland's prowess at Euro 2016 owed much to defensive excellence as they only conceded two goals in five games. Their subsequent fortunes suggest a repeat is unlikely, making it all the more important they prove prolific. Their form in friendlies, including defeats to Mexico and Nigeria, is not auspicious. With Colombia their second opponents, it is imperative they start well against Senegal. This is their first World Cup since 2006 and their best generation in three decades ought to become the first Poland side since 1986 to reach the knockout stages. But if the best-case scenario is a quarter-final appearance, a group-stage exit is also possible.
How they qualified Seemingly comfortably, winning Group D of the African section by five points after going unbeaten. Yet they had lost 2-1 to South Africa before the match was replayed and the referee banned for life for awarding a penalty for an imaginary handball. Senegal won the rearranged game 2-0.
Manager Aliou Cisse. The captain of the Senegal side who were runners-up in the 2002 Africa Cup of Nations and quarter-finalists in the World Cup. The former Birmingham City and Portsmouth player took over as Senegal manager in 2015 and has taken them to only their second World Cup.
Player to watch Sadio Mane. Finished as runner-up in the African Footballer of the Year award to his Liverpool teammate Mohamed Salah in 2017. Senegal's resident flair player is also devastatingly quick and has a capacity to excel on the big stage, as he showed with his 20th goal of the season, in the Uefa Champions League final.
Talking point Will Cisse's loyalty be rewarded? The Senegal manager called up Kara Mbodji, who missed most of the season through injury but is presumably pencilled in to form a central-defensive partnership with the outstanding Kalidou Koulibaly. Winger Keita Balde, who missed the end of Monaco's season with a hamstring injury, was also selected. Striker Oumar Niasse was a notable omission, meaning there could be an emphasis on Diafra Sakho and the veteran Moussa Sow to get the goals if Mane does not. Cisse's argument is that he was being fair to the players who served him well in qualifying.
Prediction Can Senegal repeat their heroics of 2002? There are some similarities, and not just Cisse's presence. Once again, they face the group's top seeds first, with victory over France the springboard 16 years ago and a meeting with Poland now. A physically powerful midfield, with Idrissa Gueye, Cheikhou Kouyate and Badou N'Diaye, looks a strength. Koulibaly and Mane are other trump cards and if too many underestimated Senegal in their first World Cup, they should not in their second. After Egypt, they have Africa's best chance of reaching the knockout stages. The first two games offer the greatest opportunity to get points.
Group H overview
Probably the hardest group to predict. It is possible to envisage any combination of teams going through, though Colombia look the strongest side, followed by Poland and then Senegal. Yet the pivotal game in the group could be the first, Poland against Senegal on June 19. It has the potential to reshape expectations while Colombia, who have Japan first and the potentially tougher tests thereafter, should see the imperative of a winning start. As the group winners will face the runners-up in Group G – potentially England – they will see a path to the quarter-finals, so the battle to top the pool should go down to the final fixtures.