Walmart's (WMT) - Get Report business has without question taken a hit in recent years from Amazon's (AMZN) - Get Report maniacal focus on keeping prices as low as possible and the constant stream of new services to make shopping easier.

But so far this year, the world's largest retailer has upped its e-commerce game as it, too, attempts to be viewed as a top destination for increasingly digitally-savvy shoppers.

Starting Monday and lasting until Friday, Walmart, for example, will offer free shipping with no minimum purchase on all online orders. The promotion comes in advance of Amazon's much ballyhooed "Prime Day" of special deals, which kicks off on Tuesday.

Prime Day is an exclusive sales event for members of Amazon Prime that Amazon is promoting as offering better discounts than on Black Friday. According to ChannelAdvisor, sales in the U.S. surged 93% on Prime Day last year, and by an equally impressive 53% in Europe. According to JP Morgan, last year's inaugural Prime Day drove an additional $400 million in revenue for Amazon.

TheStreet takes a look at two other ways Walmart is going on the offensive against Amazon. If mighty Walmart can make tangible inroads against the hard-charging Amazon online, perhaps the next five years will be different for the two company's respective shareholders -- shares of Amazon have gained about 250% since mid-2011 compared to just a 38% gain for Walmart.   

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1. Shipping Subscription Service

In May, Walmart launched a test of a two-day shipping subscription service called ShippingPass that mirrors Amazon's successful Prime service. Members of ShippingPass get free two-day shipping for $49 a year, compared to $99 (or $10.99 a month) for Amazon Prime. Walmart began offering a free 30-day trial of ShippingPass in early July (Amazon also offers a free 30-day trial of Amazon Prime to prospective customers). A Walmart spokesman told TheStreet that daily sign-ups to ShippingPass have more than quadrupled since the free trial offer went into effect.

2. Digital Grocery Shopping 

Walmart has quietly been expanding its new grocery pickup service this year. Customers place their grocery orders online, choose a time to pick them up and then pull into a designated parking spot when arriving at the store. From there, a Walmart worker brings the groceries to the person's car. 

The number of stores with the service now numbers over 200, following recent expansions into Charlotte, NC; Kansas City; Austin, Texas; Boise, Idaho; Richmond and Virginia Beach, Va.; Provo, Utah; Daphne, Ala.; and Charleston, S.C. 

So far, online grocery appears to have been successful for Walmart, which continues to report mixed same-store sales growth as more people shop online and move to urban areas. About 90% of its online grocery users are repeat customers, and more than 90% of the orders include fresh grocery items such as dairy, produce and meat, the company toldTheStreet in April.

Meanwhile, Amazon has also sought to deliver groceries more quickly to consumers. AmazonFresh, the Internet giant's online grocery business that originally rolled out in Seattle in 2007, delivers groceries straight to a person's house within hours. To access the service, a person needs a Prime Fresh subscription that costs $299 a year, and order minimums are $50.

The service recently launched in select neighborhoods in Boston, Massachusetts. The city joins other AmazonFresh markets in the U.S., including Seattle, Northern California, Southern California, the New York metro area, Northern New Jersey, the Philadelphia metro area, Stamford, CT and Baltimore.