The animations that follow show each of the phases:

Phase 1: 11.15-13.25
Phase 2 Reno: 13.25-15.20
Phase 2 Custer: 13.25-15.20
Phase 3 Custer: 15.25-15.45
Phase 3 Reno: 15.25-18.45
Phase 1b: Benteen and Pack trains: 11.15-16.05

This is probably the best order to view them.

Each of the animations are defined in two ways:

SVG Declarative Animation. Click SVG
Should run on most browsers other than older ones
GSAP Javascript Animation: Click GSAP
This animation uses GreenSock's GSAP Javascript library that emulates the SVG declarative animation. This should run in all browsers including Edge.

It depends on the browser and computer used which of the two performs the best.