Walmart’s recent change to free two-day shipping for online orders, no membership required, is the latest in a series of moves the company has made to fight Amazon and grow its e-commerce business. Last year, it purchased Jet.com and installed Jet’s founder, Marc Lore, as head of its e-commerce division. It has also been acquiring e-commerce niche players, including Shoebuy and outdoor gear retailer Moosejaw, and digital technology companies, such as search experts Adchemy and cloud platform OneOps.