Could 1000 armies defeat 1500 in Risk?

yes it is possible

Attacker: one die; Defender: one die:

Attacker wins 15 out of 36 (41.67 %)

Defender wins 21 out of 36 (58.33 %)

Attacker: two dice; Defender: one die:

Attacker wins 125 out of 216 (57.87 %)

Defender wins 91 out of 216 (42.13 %)

Attacker: three dice; Defender: one die:

Attacker wins 855 out of 1296 (65.97 %)

Defender wins 441 out of 1296 (34.03 %)

Attacker: one die; Defender: two dice:

Attacker wins 55 out of 216 (25.46 %)

Defender wins 161 out of 216 (74.54 %)

Attacker: two dice; Defender: two dice:

Attacker wins both: 295 out of 1296 (22.76 %)

Defender wins both: 581 out of 1296 (44.83 %)

Both win one: 420 out of 1296 (32.41 %)

Attacker: three dice; Defender: two dice:

Attacker wins both: 2890 out of 7776 (37.17 %)

Defender wins both: 2275 out of 7776 (29.26 %)

Both win one: 2611 out of 7776 (33.58 %)

from a web site

basically, it all depends on the dice

I love risk! it could happen but about 15 percent odds

yes it could depense on what you got in your army

it could happen........ but the oods are it wouldnt happen