Answer by taking a quote from the following article:

Kansas is an American rock band that became popular in the 1970s initially on album-oriented rock charts and later with hit singles such as "Carry On Wayward Son" and "Dust in the Wind". The band has produced nine gold albums, three multi-platinum albums (Leftoverture 6x, Point of Know Return 4x, The Best of Kansas 4x), one other platinum studio album (Monolith), one platinum live double album (Two for the Show), and a million-selling single, "Dust in the Wind". Kansas appeared on the Billboard charts for over 200 weeks throughout the 1970s and 1980s and played to sold-out arenas and stadiums throughout North America, Europe and Japan. "Carry On Wayward Son" was the second-most-played track on US classic rock radio in 1995 and No. 1 in 1997.

In July 1985 the band came back together with Ehart, Williams and Walsh (who had briefly played keyboards on the road for Cheap Trick in the spring and summer of 1985 after the break up of Streets), but without Livgren, Hope or Steinhardt. The new lineup included Streets bassist Billy Greer and guitarist Steve Morse (formerly of the Dixie Dregs). The first performances of the new lineup with Morse and Greer took place during a third USO 1st Airborne Rock and Roll Division tour that toured US military bases in the US, Japan, Okinawa, the Philippines, Singapore, Iceland and most of Europe during the late summer through early October 1986.  The re-formed band released Power in November 1986. The first single, "All I Wanted", became the last Kansas single to hit the Billboard Top 40 chart, peaking at No. 19. It also received considerable airplay on MTV. Two more singles, the title track and "Can't Cry Anymore", were less successful, "Power" hitting the lower end of the Hot 100 and getting substantial play and charting on the Rock Charts, but "Can't Cry Anymore" receiving little airplay despite a clever music video.  The band added New Orleans native Greg Robert on keyboards and back-up vocals at the suggestion of LeRoux's Leon Medica. Greg played his first show with Kansas on January 31, 1987 at Roberto Clemente Stadium in Puerto Rico. The new lineup released a second album, In the Spirit of Things, in October 1988. The concept album and subsequent tour were popular with the fan base but did not receive widespread airplay beyond the "Stand Beside Me" video on MTV. Morse temporarily left the band at the end of a tour of Germany in April 1989.  On September 15, 1990, Walsh, Williams and Ehart played a charity event at the Saddlerock Ranch in Malibu, California, alongside Saga, Lou Gramm (of Foreigner), Mr. Big, Eddie Money, Kevin Cronin (from REO Speedwagon) and others. Alex Lifeson joined them on stage for a short set of Kansas before Geddy Lee flew in to join Alex for a Rush set, with Ehart on drums subbing for Neil Peart.  In November 1990 a German promoter arranged to reunite all the original members of Kansas (except for Steinhardt) for a European tour. Greer joined them, along with keyboardist Greg Robert. At the end of the tour, Hope left again, but Livgren remained on into 1991.

What was the reformation?
The new lineup included Streets bassist Billy Greer and guitarist Steve Morse (formerly of the Dixie Dregs).